#1 Add possibility to change resolution/fullscreen toggle

[Peter Asplund]

Add possibility to change resolution/fullscreen toggle in the menu. The game will have to be restarted after it though, but that is ok. This also means that we need some sort of "config.file" to handle settings.

But perhaps that is about time?

Another solution is to have a fixed resolution for the menu, and the user then changes the resolution for the actual game, which is applied when user presses "Play".