Updates GameEntityManager to use GameModel instead of Game

Game class is deleted, GameModel takes its place. GameEntityManager is updated accordingly.

Authors: nfbrown dbeckwith
Merge branch 'feature-entitymanager' of https://github.com/dbeckwith/wpi-suite into feature-entitymanager

Author: nfbrown
Fixes merge conflicts

Changes all constructors for GameModel so that an ID number is the first parameter.

Author: nfbrown