Cloak and Cooldown

I've added the final powerups to the game for now. You can get cloaking, which makes lasers go through you, and you can get a cooldown powerup which makes your regenerating and other abilities work faster. I'll probably add some modifications to how that all works later.

I also made another change to the missile vs laser dynamics. Lasers still destroy missiles without being destroyed, but lasers have gone back to passing through each other.

So now lasers trump missiles trump shields trump lasers. Which is a good roshambo dynamic, which adds value both the the game and the ALife aspects of Trilobots.

Next on the agenda: Scoring!