Add multi-functional button (new game, pause, unpause)

https://bugzilla.gnome.org/show_bug.cgi?id=710620
Remove toolbar and fullscreen mode

https://bugzilla.gnome.org/show_bug.cgi?id=710620
Change GTK dependency to 3.10
Add headerbar window

https://bugzilla.gnome.org/show_bug.cgi?id=722228
Change default window size to something nicer looking