Level Up! Reloaded

This mod now uses Mixin to hook into vanilla code, which should make the furnace and brewing stand skills process much faster than through the event channels.

Furnace speed now directly affects cooking speed, reducing time by 20 ticks per level. Hooked into the getCookTime method.

Furnace doubling now happens during the smeltItem method, providing instant doubling instead of the "one tick delay."

Brewing stand processing happens during the start of the update method.

Special compatibility for FastFurnace, because it overrides the smeltItem method.