Avoid code duplication in the cuboid code

Boo code dupping
Make cuboid's cu@ optional

We don't /need/ a cu@
Complain less when NPCs go away

No need to flood the console if NPCs are being deleted.
Make modifyblock take ellipsoid and cuboid arguments

Quicker large-region block edits
Merge pull request #909 from mcmonkey4eva/master

Pull request for some minor things