Picture handling: change data structure to store offset instead timestamp

It makes no sense to store a 64bit time stamp with every picture. Even the
32bit offset (in seconds) from the dive start is WAY overkill. But
switching to that makes the code much more simple in a number of spots.
And makes what is saved to the XML file easier to read, too.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Picture handling: parse XML data

Using XML data files we can now save picture data and load it back in
again. The corresponding code for save-git and load-git is still missing.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Pick the correct API function name for Qt5

Subtle change in function name from Qt4 to Qt5

setAcceptsHoverEvents -> setAcceptHoverEvents

Now Subsurface builds with Qt5 again.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Simplify the code that checks if it's OK to close the current file

And make sure it gets called whenever it needs to get called - it was
missing from the openRecentFile case.

Fixes #530

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Display liters with script el

Use script ell instead of 'l' for liters to avoid confusion with digit 1.
Let's hope that this glyph is available in the common fonts, otherwise
we'll have to revert it.

[Dirk Hohndel: split commit into two]

Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Planner: incease step size in deco ascends to 3 seconds

Triple time step in deco ascents to improve responsiveness of interactive
deco calculation.

[Dirk Hohndel: split commit into two]

Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Really display liters with script el

In commit 125ddd955c04 ("Display liters with script el") Robert only fixed
the C routine we use to show units. Strangely, we had a separately
implemented C++ function as well. Instead of implementing this in two
spots I now simply have the C++ function use the C function to do the
actual work and then wrap this into an easier to use (from UI code)
QString output.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Change character for liter in SAC values as well

And fix the bug that in the info overlay SAC was always given in metric
values. And try to reduce the number of places in which we calculate the
unit conversions...

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