ENH: use SegmentDescription to populate SegmentLabel

This will be done when SegmentLabel is not passed in configuration.
SegmentDescription is better than using CodeMeaning from SegmentationType,
as it allows more precise control by the user.

libsrc/Itk2DicomConverter.cpp

@@ -245,6 +245,9 @@ namespace dcmqi {
         if(segmentAttributes->getSegmentLabel().length() > 0){
           cout << "Populating segment label to " << segmentAttributes->getSegmentLabel() << endl;
           segmentLabel = segmentAttributes->getSegmentLabel().c_str();
+        } else if(segmentAttributes->getSegmentDescription().length() > 0){
+          cout << "Populating segment label from SegmentDescription to " << segmentAttributes->getSegmentDescription() << endl;
+          segmentLabel = segmentAttributes->getSegmentDescription().c_str();
         } else
           CHECK_COND(typeCode->getCodeMeaning(segmentLabel));