Re-add melting down of tool parts

The reason I disabled them was so that players didn't just walk into a town, grab the TiC building's toolparts, and make a metal pickaxe from almost no effort.

Now that village generation is disabled, there shouldn't be any chance of metal tool parts being found (at least early on), and therefore I can re-enable their melting recipes.

Also added the melting down of cobalt, ardite, and manyullyn ingots and shards in a smeltery, because as of right now there isn't a way to alloy the two together.  Until I find a better way to do so, melting down processed nether metals will have to do.