Quit Subsurface with yearly stats window in front

Add ability to quit Subsurface with a Ctrl-Q shortcut even if the yearly
statistics window is active.

Signed-off-by: Miika Turkia <miika.turkia@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
User manual: some changes regarding the companion app

Subsurface companion is, basically, the same from last Subsurface release,
it's only been added with the map feature which is depicted here.

Distance between positions takes precedence over time between them, so you
can have positions faster than one each period set in the "Min Duration"
setting.  Actually this setting seems useless as you won't have a fix each
period if distance is under "Min distance".

Lesser changes in manual involving Background Service, the dificulty on
matching times and little personal recomendations.

[Dirk Hohndel: minor language changes]

Signed-off-by: Salvador Cuñat <salvador.cunat@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Closing about window by shortcut

This adds the ability to close the about window with the ctrl + w
shortcut.

Signed-off-by: Gehad elrobey <gehadelrobey@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Quit Subsurface with about window in front

Add ability to quit Subsurface with a Ctrl-Q shortcut even if the about
window is active.

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