Documentation game.model

* Documentation for:
game.model.Door
game.model.Entity
game.model.Position
game.model.SpotAnimation
game.model.shop.GeneralStore
game.model.shop.Shop
game.model.shop.StockType
game.model.shop.StockedShop
* Format
game.model.player.ShopHandler (I moved an if statement as well :P).