Various MCP-branch fixes

Hopefully these commit and compile well -- rebase messes up sometimes and I can't compile the base mcp code as-is because forge-mcp moves all the minecraft classes into packages.

Includes iluvredwall's even-stacks code, fixes to some modcompatibility issues, a fix for items being moved when you open an inventory, and a fix for armor-replacement not handling things like skulls that are not ItemArmor but are wearable correctly.