ENH: add support of DCMTK private dictionary
Created by: fedorov
See issue 4013 and related discussion here:
http://slicer-devel.65872.n3.nabble.com/Enabling-support-for-DCMTK-private-dictionary-td4034305.html
This change installs private.dic of DCMTK in a runtime location, and sets DCMDICTPATH launcher variable. This will allow for more robust interpretation of DICOM private tags based on the information contained in the DCMTK private dictionary.