Fix widget sizes in navigation bar

Toolbar does not belong in this size group. It's causing all the widgets
in the navigation bar to expand super wide, which looks terrible.
Compute the width of the time labels at runtime

Set the time labels to be a little bit wider than the widest they might
ever be, so they never resize.

This assumes that each player will be limited to at most 999 minutes,
which currently is not the case, but will be soon.

https://bugzilla.gnome.org/show_bug.cgi?id=726955
Workaround signal misfires that led to crash

Even though the original ChessGame is always destroyed immediately after
the creation of a new one (no other reference to it exists), the signals
we connected to the original game may be nonetheless fired by the NEW
game object. This must be a bug in Vala signals.

https://bugzilla.gnome.org/show_bug.cgi?id=732037
Prepare 3.10.4
Do not enable pause action when browsing history

If a game is already completed, moving around in history could cause the
pause button to become sensitive.
Simplified Chinese: fix desktop file keywords