ENH: Adding SPHARM-PDM extension to the SlicerExtension index

Shape analysis has become of increasing interest to the medical community due to its potential to precisely locate morphological changes between healthy and pathological structures. SPHARM-PDM is a tool that computes point-based models using a parametric boundary description for the computing of Shape analysis.
The point-based models computed with the SPHARM-PDM tool can be used in combination with the also UNC designed statistical tool shapeAnalysisMANCOVA to perform quantitative morphological assessment of structural changes at speciﬁc locations.

Authors Beatriz Paniagua (UNC), Francois Budin (UNC), Martin Styner (UNC)
Merge pull request #570 from fbudin69500/add-SPHARM-PDM-4.3

ENH: Adding SPHARM-PDM extension to the SlicerExtension index