"un-hardcode" furnace

[samuellsk]

if possible with some options like:

• smelt only specific material (for example iron only furnace)
• smelt everything up to "adamatium" (smelts everything down that is up to specified material level , like adamantium)
• if created with glyphs , remove them (but item would be destroyed not smelted down to materials)

[KA101]

This'd help mod support, particularly mods that add new gear and metal ores. If nothing else, having the furnace pick up its resource-cost list from the forging end of things (so if it can be crafted at a forge, it can be smelted to return half the crafting material at a furnace;) would greatly streamline modding.