Add MOD and MND fields to cylindermodel

Adds fields to the planner cylinder model for maximum operating depth (MOD)
for a bottom mix gas, and maximum narcotic depth (MND). Fields are read/write,
so changing MOD changes %O2 and vice-versa. Changing MND changes %He and
vice-versa.

When setting MOD directly, the %O2 is truncated (rounded down) to an integer,
which re-calculates the MOD, which is sometimes a few metres greater than the
input depth. This is desireable behaviour, as the rounding is conservative.

Signed-off-by: Rick Walsh <rickmwalsh@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

qt-models/cylindermodel.h

@@ -19,6 +19,8 @@ public:
 		O2,
 		HE,
 		DEPTH,
+		MOD,
+		MND,
 		USE,
 		COLUMNS
 	};