Fixed the bug in BlockDimWall that would cause Fabric of Reality to
replace itself when you right-clicked to place FoR against an FoR
surface. This happened because we considered FoR valid for replacing FoR
since it's a cube solid. Now we have an extra check to prevent that. It
was a waste of blocks to have them sort of eat each other up! Also
cleaned up some of the code in BlockDimWall.
71adfa2358