Remove World Generation

[Luthervian]

I think it would be great to be able to have a mod.RemoveWorldGen that is capable of removing the spawning of a particular item from world generation.

For instance:

mod.RemoveWorldGen(15) would remove iron from being generated in a world.

While ideally, it'd be better to be able to adjust the generation of Vanilla blocks (as the mod Custom Ore Gen used to do), this would present a workaround as I could then simply make a new WorldGen file for Iron.

[cubex2]

Added mod.removeMinable() and mod.removeBiomeDecoration()