Boardmodel refactoring

A few changes in preparation of a big cleanup..

There is a fair amount of duplication with regards to p0/p1 methods. I've inserted references to current/waiting player, and already removed some duplication as a result in Game.java. I should be able to do a really big cleanup of gamemodel (formerly gamestate) on top of this.

Also, a few minor things:
- tried to pull player class into the boardstate/model as it didn't have much purpose outside of it and is tightly coupled to it anyways.
- renamed state to model. makes sense to me this way as it's a model of the board, w/ methods to manipulate. When I think state I just think data, or maybe data plus state transitions. Could rename it back if it's a problem.