Add CMFreg extension

A registration package oriented to the Dental Research community. The package will perform superimposition using diverse Cranio-Maxillofacial CMF areas as stable regions of reference. This package provides several modules: mathematical operations on label maps, mask creation and non-growing/growing registrations.

http://www.slicer.org/slicerWiki/index.php/Documentation/Nightly/Extensions/CMFreg