Added loader which loads external files, not working properly so may
remove. Added main menu, multiplayer just goes to singleplayer for now.
Moved levels into separate .js file for easy editing and changed
structure for procedural level generation. Other minor changes.
Added more to base of new physics with level, removed orange square,
added new particle, added enemy actor, added mouse detection, added
health and coordinate info at bottom, changed sprites to simpler look
with different colours, added reflection fade away, made acceleration
and deceleration higher for better control, and added a reticule for the
mouse.
