Changes to AssetManager, Textures, Meshes, Engine

AssetManager:
AssetManager changed to AssetLoader, only a convenience class for calling asset specific methods.
Textures:
Textures are referred to by path, until execution of the game.
Meshes:
Meshes are referred to by path, until execution of the game.
Engine:
Games now extend BaseGame instead of initiating a new Engine object.