Added different states managed by Game.
You start on the main menu. Click the button to go to the game.
You can also use numpad 7 to start the level and 8 to go back to the main menu.
Put layers in their corresponding class. Layers that were in Game are now in Level. Mainmenu has its own layers.
Merge branch 'master' of https://github.com/AWhiteRose1142/stronghold

Conflicts:
	input_manager.lua