Retooled draw manager (now it uses an array of lists so we don't end up with sprites overdrawing other sprites when we don't want them to). It's a bit broken right now and I'm not sure why (that is, some background tiles are drawn over the player for some reason - look into later). Also added a basic camera which follows the player (though the player is up in the corner because I haven't quite figured out how to get it to shift to the center yet). Added a player manager and a few things dealing with multiplayer. Added a boolean flag to mobile entity to keep track whether or not an entity is active (used only for the player right now, but could be useful elsewhere). Also added another, currently stubbed out method to GameState for going to the next state, though it's not used right now.