mobile/dive summary: rewrite statistics code

There were quite a few issues with the code - clearly a complete failure of
code review.

- all values were '??' if a period contained no dives
- imperial units were not calculated at all
- significant truncation and data loss in the way totals were added as meters
  and minutes instead of the higher precision data that is available
- several issues in striing conversion methodology, e.g. missing zero padding
  for minutes
- missing maxSac
- incorrectly calculated avgSac
- incorrectly claculated number of EANx dives
- hard to read code with most variables named 'temp'

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

mobile-widgets/qml/DiveSummary.qml

@@ -181,7 +181,7 @@ Kirigami.ScrollablePage {
 			text: Backend.diveSummaryText[19]
 		}
 		TemplateLabel {
-			text: qsTr("avg. SAC")
+			text: qsTr("max. SAC")
 			font.bold: true
 		}
 		TemplateLabel {
@@ -190,6 +190,16 @@ Kirigami.ScrollablePage {
 		TemplateLabel {
 			text: Backend.diveSummaryText[21]
 		}
+		TemplateLabel {
+			text: qsTr("avg. SAC")
+			font.bold: true
+		}
+		TemplateLabel {
+			text: Backend.diveSummaryText[22]
+		}
+		TemplateLabel {
+			text: Backend.diveSummaryText[23]
+		}
 
 		TemplateLabel {
 			Layout.columnSpan: 3
@@ -200,10 +210,10 @@ Kirigami.ScrollablePage {
 			font.bold: true
 		}
 		TemplateLabel {
-			text: Backend.diveSummaryText[22]
+			text: Backend.diveSummaryText[24]
 		}
 		TemplateLabel {
-			text: Backend.diveSummaryText[23]
+			text: Backend.diveSummaryText[25]
 		}
 
 	}