Main menu background animations

[lemonsaurus]

The main menu would look a lot better if it had a little animation.

Let's do the following two things:

• Make the LemonCop's tongue and mouth move, like he's screaming.
• Make the duckies in the background swim around.

This will probably require rendering these things in the game engine rather than using a static background image. It might also need graphics with some elements removed, so that these can be rendered in-game.