add path tracker

src/python/dm/ds_web_service/service/impl/pathTracker.py

+#!/usr/bin/env python
+
+from dm.common.utility.objectTracker import ObjectTracker
+
+class PathTracker(ObjectTracker):
+
+    # Cache configuration
+    pass
+
+####################################################################
+# Testing
+
+if __name__ == '__main__':
+    et = PathTracker.getInstance()
+    print et
+    et2 = PathTracker.getInstance()
+    print et2
+    et.put('xyz', 1)
+    print et.get('xyz')
+    print et.get('xyz2')
+
+
+