MeshModifier for defining new SubdomainIDs inside of bounding box

* I had a good friend call and ask if MOOSE could solve a particular problem, I said sure, this feature will help be show him that it can.

* There is one problem that I don't know how to address: if someone changes the entire domain the created block 0 hangs around in MOOSE causing problems with defining materials. I am not sure what I need to reset within MOOSE for this case.

(#3220)