Multiplayer Gameplay

Did a (poor) attempt at multiplayer AI. The Army powerup enables an
extra paddle with CPU AI for the colored player. Paddles seems to like
converging towards each other towards the pucks simultaneously, and
getting the puck stuck in each other. Also, guarding the goal is not
working entirely (paddles are supposed to puppy guard their goal, and
lock on to the puck's z position at the goal).

Need to get proper collision working, probably without using our 6
sphere collision hack, in order to fix these problems. I'll try
replicating the behavior I used in the original 2D UAH game.