Rooms can "dig in" to a certain extent. Gardens/Paths now fill 1 down
into the room below with a foundation material (secondary).
Bug in replace which caused *everything* to be replaced with
stone/cracked/moss if stone was set, fixed.
Fix - or rather sidestep - of intersection bug, by intersecting
buildings rather than rooms in Castle.intersect(). There's still a
problem there - perhaps some rooms aren't being added to the system?
room add sanity check (commented out)
Merge remote-tracking branch 'origin/master'