Add Level class to store level data, for example soundMap, physicsMap etc
Add with mediator.levels an object dictionairy that holds all loaded Levels
Add with mediator.activeLevel a string that is the key to the level the Player is playing in the mediator.levels dict
Modified MapInitialEntitySpawnManager, PhysicsManager, SoundManager and TiledMap so they use the level class instead of @ (home-page-view and managers); this means we are now able to load levels without overwriting exiting levels
Add stopAll method to SoundManager to be stop all playing sounds; needed later when the Player moves to another level
Add event: 'levelChangeTo:'+LEVEL, where LEVEL is the level to change to
Modify event: 'map:rendered' to 'mapRendered:'+LEVEL
Modify event: 'sound:loaded' to 'soundsLoaded:'+LEVEL
Note: redundancies and confusing names will be fixed later combined with a detailed documentation