Added a few functionalities to Game.java and created basic AI's.

Created by: MaurizioBruetsch

The board gets printed after every move, and the game continues until the board is full, this isn't actually checked, the game continues until one of the players doesn't propose a valid move, which should be changed. Preferrably so that after every move somebody checks whether there is a winner. The AIs are rather simple minded, but if possible they make a valid move.