Make ItemBuilder able to incorporate existing ItemStacks and modify them

[lokka30]

I'll pile my current (lack of) thoughts here:

• Do not try to recreate the itemstack. It should modify the itemstack as the builder is used, and return the itemstack object on build.
• Clone the itemstack when modifying it.

[HSGamer]

I guess it could be something like this

[lokka30]

I guess it could be something like this

That's a very cool item builder! Thanks.

I can't remember why I added an item builder class - I think it was just for MicroLib parity - so I might remove my ItemBuilder if I don't have a use for it (which means that I would have found a nice GUI library).