This is cleaner and easier than calling into the gtk builder directly.
I bumped up the window layer so other gui components can use it.
Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>
Saving maximized state is too complicated, so let's just store width and
height of the window when it is not maximized.
Signed-off-by: Anna Schumaker <Anna@OcarinaProject.net>