MCL Update

Re-added the previous functionality, rewrote some bits that could have been done better and removed some redundant bits. In some cases this puts a bit more work on the modder's shoulders, but its not too bad generally.

I haven't actually attempted to update Railcraft yet, so I can't promise that I didn't break/forgot something.

Vswe should probably take look at this too.

Anyway, constructive suggestions welcome.