Stacking in any direction

Because it's terribly frustrating that it's impossible to make a grand staircase mine in worldedit. 

I tested this on a server a bit with some random mixture of brick and glass, and it didn't seem to mess up the pattern, so I think it's correctly copying with overlap (i.e. not using a copied block as a source to copy from).

I added in a randomized /set so that /luatransform thing isn't needed. Also fixed and heavily tested /stack2. Not sure if there's a place I can put screenshots here, but:

http://imgur.com/a/d9zZQ