Further Customization Capabilities

Well, there are pretty substantial custom entity editing capabilities now. I'd love to provide facilities for a completely-from-scratch entity, but that would require more changes to MG's base code than I want to contemplate. You can do special doors; they can be opened by key, by levers, by a mob dying, or even by entering a certain space. That's not the hard part about adding the ability to do custom boss levels. I think I've figured out a way to handle custom boss levels, so that should be in pretty soon, here.

This is added, callout for beta has been posted.