NetherBound

Completely rewrote the whole mod from the ground up. Now, instead of detecting a wither spawn and neutralizing it, it bypasses the placement of skulls, so that the vanilla code that spawns the wither is never called. This prevents it from being  canceled halfway through, which should mean no more ghost blocks. Additionally, the wither structure will be left behind, so you get a total refund from a failed spawn.

Additionally, I've disabled the ability for dispensers to place heads, to prevent the wither from being spawned outside the nether that way.