some of these (notably the on* methods) are internal and shouldn't be exposed via interface (same crap as Plugin->onEnable() onDisable() etc) and the rest of the stuff is entirely unused.
Inventory holders are now freed from BaseInventory. They are now declared by subclasses by convention, but are not required in most cases.
Ideally, this would be followed by the removal of the need for inventories to know their holders at all. They should just be simple containers of items.
This fixes#1560 by removing FakeBlockMenu.
