Pause / resume timer

[jbowens]

Allow pausing and resuming the turn timer. The interface could be as simple as clicking the timer, but maybe that's not discoverable enough.

[skgbanga]

Hey,

First, thanks for developing this great game!
I was looking for an option to have a timer in the game, but couldn't find one. I stumbled upon this issue and it seems like it is already an option? If yes, could you please let me know how to enable it? My screen looks like this:

[skgbanga]

Oops. Just saw the enable timer option before you start the game. Thanks!

[nochkin]

@jbowens,
I would like to consider implementing this feature, but the unresolved licensing issue puts it under question.
Please take a look at this PR to resolve it.