Started work on new inventory system

One inventory class, handling multiple pocket classes, handling their
items.
Added basic item moving

Moving items between pockets and stacks/bags.
Moved CheckItemMove method to CreatureInventory

*saving untested "work" of the last hour*
Splittet Inv and Pockets (cleaner)
Added picking up (untested)
Added splitting (untested)
Removed PacketCreator's ItemAmount and ItemRemove

Use Send.ItemX from now on.
Finished picking up and splitting (seemingly working)
Added dropping
Added destroying
Added missing pockets
Added switching weapon set
Added item state changing
Added buying and selling (no gold support yet)
Added equipment view
Added dyeing
Added item using
Removed references to MabiCreature.Items.cs

This is gonna be highly unstable~
Fixed NPC exceptions

that were caused by the the missing item methods
Fixed buying items

* Overflow in InventoryPocketNormal.Remove
* CreatureInventory.PutItem returning false instead of success