Dungeon generator examples

Testing with three rooms it's already clear that there are problems.

Doors are not created when there is cavern outside it. It's easy to fix I guess, but might cause confusion if two separate caverns are next to the room. The possible solution to that is giving caverns also a unique mask id.

Here is another run with the same level theme. The long narrow corridor is actually a passage, which is a special kind of corridor. It seems to have problems to turn around without backing up and generating extra dead end blocks, but it should be easy to fix.