Added multi-world inventory support.

Should maintain inventory through Nether, End and Overworld - But will change the inventory when they go to other worlds like our custom worlds Einhome, Treton etc.
Added multi-world inventory support.

Allows user to have an independent inventory for every world - Excluding Nether, End and Overworld which all share one inventory.
Merge pull request #252 from lDiverse/patch-109

Multi world inventory support.