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?
Merge pull request #13 from Domos123/master

Implemented castle layout based upon perlin noise
room add sanity check (commented out)
Merge remote-tracking branch 'origin/master'
As the documentation says we shouldn't really assign the return value of
getConfig() to a static, we don't do that any more. We certainly don't
create new instances of GormPlugin every time we want to access config!
Instead, there's a single instance which can be obtained with
GormPlugin.getInstance()
Clened up a few unnecessary instances