Added NPCs!
Made an NPC class which is pretty much the same as a player, aside form the movement methods. There will probably definitely be more differences later on.

Haven't done collision detection/resolution for NPCs. Need to make NPCs obey boundaries, and need to make NPCs collide with one another and Players.

Need methods to control NPC movement.. Maybe some NPCs will be stationary, while others follow set paths? Need interaction with NPCs.

Need mobs.