COMP: Start using ITKConsortium github to retrieve DCMTK.

Change-Id: I078b5374b9b66a7d4cc2a4c4030a911f1be4e8aa
Merge topic 'USE_ITKConsortium_Githug_Repo_DCMTK'

83e6649 COMP: Start using ITKConsortium github to retrieve DCMTK.