Text cleanup to amend lacking consistency

- Removed the "Visible:" header on the column selector.  It doesn't
  have to be there, and it's not in the similar equipment column selector
- PO2 --> pO₂ (and others)
- Use same initial case in the units selector in preferences

Signed-off-by: Henrik Brautaset Aronsen <subsurface@henrik.synth.no>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Make sure the save/cancel message is always shown

An addition to the "Move dive notes edit message above the
scrollable widget" commit:  Make sure the save/cancel message is
always displayed on top, regardless of which tab is selected.

Signed-off-by: Henrik Brautaset Aronsen <subsurface@henrik.synth.no>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
qmake: Fix unescaped backslashes issues

We need to espace the backslash with '\\' on win32.

Signed-off-by: Lubomir I. Ivanov <neolit123@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
qmake: fix a 'GIT_DIR' issue

"'GIT_DIR' is not recognized as an internal or external command",
is reported if qmake is runned on Win32.

To solve that we set a explicit syntax for Win32 that uses "Set.."

Signed-off-by: Lubomir I. Ivanov <neolit123@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
qmake: use real tabs for all .pri files

subsurface.pro already useses that.

For consistency with the app, we use swap 4 spaces with
a tab character for indentation.

Signed-off-by: Lubomir I. Ivanov <neolit123@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Update to user manual

Made changes to dive profile section.

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