Ender Furnace: Add more buttons and update the GUI texture and slot positions.
Ender Furnace: Add the buttons to the GUI, some texture tweaks.

The buttons don't do anything yet, and their state/texture is not based
on the actual state of anything.
Ender Furnace: More progress on the GUI/buttons. Now they work and update.
Ender Furnace: Add owner data when placing. Add some NBT data read/write stuff.
Ender Furnace: Use getDescriptionPacket() + onDataPacket() for mode changes.
Ender Furnace: Add the smelting logic (mostly).

Doesn't have the bigger custom output buffer/slot yet.
Also output to Ender Chest is missing still.