User manual spelling errors

I finaly got a a spelling checker that operates on asciidoc files.
I am relieved that this only found about a dozen spelling errors
in the whole text.

Signed-off-by: Willem Ferguson <willemferguson@zoology.up.ac.za>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

Documentation/user-manual.txt

@@ -443,7 +443,7 @@ Check the following:
    USB port? If not, consult
    xref:_appendix_a_operating_system_specific_information_for_importing_dive_information_from_a_dive_computer[Appendix A]
 
-If the _Subsurface_ computer does not recognize the USB adaptor by
+If the _Subsurface_ computer does not recognize the USB adapter by
 showing an appropriate device name next to the Mount Point, then there is a
 possibility the cable or USB adaptor is faulty. A faulty cable is the most
 common cause of communication failure between a dive computer and _Subsurface_.
@@ -499,7 +499,7 @@ four steps:
 
 Select the Download dialogue by selecting
 _Import -> Import from dive computer_ from the *Main Menu*. After checking the
-box labelled _"Choose Bluetooth download mode"_, the dialogue below appears.
+box labeled _"Choose Bluetooth download mode"_, the dialogue below appears.
 
 ===== On Linux or MacOS:
 
@@ -507,8 +507,10 @@ image::images/DC_import_Bluetooth.jpg["FIGURE: Download Bluetooth",align="center
 
 Although the _Subsurface_ Bluetooth interface is intended to function without
 Bluetooth pairing at the operating system level, it is always prudent to follow up
-initial Bluetooth pairing problems by pairing the Bluetooth dive computer with the _Subsurface_ computer using the operating system services of the desktop computer. Delete all
-existing pairings and start by scanning for Bluetooth devices from an empty list (on the desktop) of Bluetooth devices. Once _Subsurface_ has recognised the Bluetooth dive
+initial Bluetooth pairing problems by pairing the Bluetooth dive computer with
+the _Subsurface_ computer using the operating system services of the desktop computer. Delete all
+existing pairings and start by scanning for Bluetooth devices from an empty list
+(on the desktop) of Bluetooth devices. Once _Subsurface_ has recognised the Bluetooth dive
 computer, subsequent divelog downloads are likely to be simple.
 
 On the _Linux_ or _MacOS_ platforms the name
@@ -2069,7 +2071,7 @@ for more complete information. Use that software to download the dive data into
 a known directory. From the main menu of _Subsurface_, select _Import ->  Import
 log files_ to bring up the xref:Unified_import[universal import dialogue]. As
 explained in that section, the bottom right
-hand of the import dialogue contains a dropdown list (labled _Filter:_) of appropriate devices
+hand of the import dialogue contains a dropdown list (labeled _Filter:_) of appropriate devices
 that currently include (Poseidon) MkVI or APD log viewer files. Import for other
 CCR equipment is under active development. Having selected the appropriate CCR format and
 the directory where the original dive logs have been stored from the CCR dive
@@ -2345,11 +2347,11 @@ values are dependent on the composition of the breathing gas. The EAD
 is the depth of a hypothetical air dive that has the same partial
 pressure of nitrogen as the current depth of the nitrox dive at
 hand. A nitrox dive leads to the same decompression obligation as an
-air dive to the depth equalling the EAD. The END is the depth of a
+air dive to the depth equaling the EAD. The END is the depth of a
 hypothetical air dive that has the same sum of partial pressures of
 the narcotic gases nitrogen and oxygen as the current trimix dive. A
 trimix diver can expect the same narcotic effect as a diver breathing
-air diving at a depth equalling the END.
+air diving at a depth equaling the END.
 
 Figure (*B*) above shows an information box with a nearly complete set of data.
 
@@ -2460,7 +2462,7 @@ Show the partial pressure of *nitrogen* during the dive.
 [icon="images/icons/He.jpg"]
 [NOTE]
 Display of the partial pressure of *helium* during the dive.
-This is only important to divers using Trimix, Helitrox or similar breathing gasses.
+This is only important to divers using Trimix, Helitrox or similar breathing gases.
 
 The *air consumption* graph displays the tank pressure and its change during the
 dive. The air consumption takes depth into account so that even when manually
@@ -2600,7 +2602,7 @@ for more details on the different elements of this graph.
 
 Image *B* shows a gradient of unique colours, spanning the whole range of inert gas pressures.
 It is possible to map the height of each of the dark green vertical bars of *A* to a
-colour in *B*. For instance, the fastest (leftmost) dark green verical bar in *A* has
+colour in *B*. For instance, the fastest (leftmost) dark green vertical bar in *A* has
 a height corresponding to the medium green part of *B*. The height of this bar can therefore be summarised
 using a medium green colour. Similarly, the highest dark green bar in *A* is as high
 as the yellow part of *B*. The 14 remaining tissue pressure bars in *A* can also be
@@ -2731,7 +2733,7 @@ just before or after the dive, or of landscapes as seen from the boat.
 
 [icon="images/icons/inAndOutPhoto.png"]
 [NOTE]
-This dive has photographs taken both during the dive and immdiately before or after the dive.
+This dive has photographs taken both during the dive and immediately before or after the dive.
 
 [[S_Renumber]]
 === Renumbering the dives
@@ -3619,7 +3621,7 @@ the nitrogen load incurred during previous dives.
 
 - Define the depth of the dive by dragging the waypoints (white dots) on the dive profile or
   (even better) defining the appropriate depths using the table under _Dive planner points_ as
-  desribed under the previous heading. If
+  described under the previous heading. If
   this is a multilevel dive, set the appropriate dive depths to represent the dive plan by adding
   waypoints to the dive profile or by adding appropriate dive planner points to the _Dive Planner Points_
   table. _Subsurface_ will automatically extend the bottom section of the dive to the maximum
@@ -3716,7 +3718,7 @@ the limit of the gas supply but that an appropriate reserve is kept
 for unforeseen circumstances.
 For technical diving, this reserve can be up to 66% of the total available gas.
 In addition to calculating the total gas consumption for every cylinder the planner provides one way
-of calculating the recommended volume of bottom gas which is needed for safe asscent to the
+of calculating the recommended volume of bottom gas which is needed for safe ascent to the
 first deco gas change depth or the surface. This procedure is called the "minimum gas" or "rock bottom"
 consideration and it is used by various (but not all)
 technical diving organisations. See the text below for a detailed explanation.
@@ -3825,10 +3827,10 @@ This indicates:
 The planner also estimates the *minimum gas* pressure required for safe ascent after an event that causes the dive
 to be aborted. The calculation assumes that in worst case an out of gas (OoG)
 situation occurs at the end of the planned bottom time at maximum depth. This OoG event forces
-the buddy team the share the gas of one diver and thet they require an additional period of time at maximum depth to solve the problem at hand.
+the buddy team the share the gas of one diver and that they require an additional period of time at maximum depth to solve the problem at hand.
 In addition the combined SAC of both divers is increased by an estimated factor compared to the SAC factor of a single diver under normal conditions.
 The result of the minimum gas calculation for the bottom gas is printed to the planner output. No automatic checks are performed based on this result.
-The feature only gives valid results for simple, rectengular shaped single
+The feature only gives valid results for simple, rectangular shaped single
 level dive profiles. For multi level dives one would need to check every leg of the profile independently.
 
 There are two selector boxes on the left of the _Dive plan details_:
@@ -3870,11 +3872,11 @@ _Open circuit_ in the dropdown list.
 The parameters of the pSCR dive can be set by selecting  _File ->   Preferences ->   Profile_
 from the main menu, where the gas consumption calculation takes into account the pSCR dump
 ratio (default 1:10) as well as the metabolic rate. The calculation also takes the oxygen drop
-accross the mouthpiece of the rebreather into account. If the
+across the mouthpiece of the rebreather into account. If the
 pO~2~ drops below what is considered safe, a warning appears in the _Dive plan
 details_. A typical pSCR cylinder setup is very similar to an open circuit dive;
-one or more drive cilinders, possibly with different bottom and decompression
-gasses, including gas switches during the dive like in open circuit diving.
+one or more drive cylinders, possibly with different bottom and decompression
+gases, including gas switches during the dive like in open circuit diving.
 Therefore, the setup of the _Available gases_ and the _Dive planner points_ tables
 are very similar to that of a open circuit dive plan, described above. However, no oxygen setpoints
 are specified for pSCR dives. Below is a dive plan for a pSCR dive. The dive is comparable
@@ -3971,11 +3973,11 @@ In order to do this:
   real-life dive from the _dive computer_.
 - In the _Dive List_, highlight the dive plan as well as the data for the real dive
   and merge the two dives, making use of the Dive List Context Menu
-  (available by righ-clicking a dive).
+  (available by right-clicking a dive).
 
 The text version of the dive plan is appended to the Notes in the _Notes Tab_. With this
 merged dive highlighted in the _Dive List_, switch
-between the planned profile and the real-life profile using the righ-arrow/left-arrow keyboard keys.
+between the planned profile and the real-life profile using the right-arrow/left-arrow keyboard keys.
 
 == Running _Subsurface_ from the command-line
 _Subsurface_ can be launched from the command-line to set some specialised settings or as