Add handling of bags on class attributes to Item similar as it is on Room

[edmw]

Not sure if this is intentional. But the room class initializer contains code to deepcopy instances of Bag from class attributes to instance variables. Which allows to define

Room.items = Bag()

and add items afterwards

room = Room(...)
room.items.add(item)

My son was using this pattern to build items which can contain other items (for example a shelf).

Because the initializer of class Item is missing that code to copy bags, this did not work as expected, because there will be only one instance of Bag for every item.

I suggest to add the same handling of bags to class Item.