Add CMFreg extension

Author: Vinicius Boen, University of Michigan
Contributors: Francois Budin (NIRAL, University of North Carolina), Martin Styner (NIRAL, University Of North Carolina), Beatriz Paniagua (NIRAL, University Of North Carolina), Lucia Cevidanes (University of Michigan - School of Dentistry)
Contact: Vinicius Boen, 
Website: http://www.slicer.org/slicerWiki/index.php/Documentation/4.3/Extensions/CMFreg