Item.cs needs to include "amount"

[JaXt0r]

In Gothic, an item on the surface is only drawn once, but can represent a batch of items. (e.g. dropping 13 ore from inventory will draw only one mesh).

We need to have a way to get the amount information from the Vob when loaded.

[lmichaelis]

@JaXt0r it's done in ff147edb9cdab5c75bc1f42a6b4e8d16f332c5ad

[JaXt0r]

Thank you.