Added keyboard control for all menus
Known bugs in keyboard control:
The scroll wheel in the resolution dropdown doesn't work.
In the Level Select screen, Level 1 is not highlighted when entering the screen. This is only a graphical issue, you can still use the keyboard for selecting.
Added a go back one level button for the pause and win menu. This button does not work in bonus levels.
Bug fix: When activating the optional win menu, the player could still move in the puzzle after completing it.