Adds a new item: Empty Disc which is crafted with 2 Flint and 1 Ender Pearl.
When you put it into a Jukebox it makes a redstone signal of 15 and it plays a short noise.
Music discs are crafted with a Empty disc in the middle and two (in case of 11 one) wools on each side. (Pigstep is the only disc which isn't crafted with wool but with netherrack and gold.)
