Added initial implementation of the Titan + Gremlin based shortest-path
computation. It replaces the existing Floodlight backend, and
can be used with the existing REST-based API.

Added a test Python-script which is just a wrapper for
the "curl" call.
diff --git a/shortest_path.py b/shortest_path.py
new file mode 100755
index 0000000..5bea182
--- /dev/null
+++ b/shortest_path.py
@@ -0,0 +1,71 @@
+#! /usr/bin/env python
+# -*- Mode: python; py-indent-offset: 4; tab-width: 8; indent-tabs-mode: t; -*-
+
+import pprint
+import os
+import sys
+import subprocess
+import json
+import argparse
+import io
+import time
+
+from flask import Flask, json, Response, render_template, make_response, request
+
+#
+# curl http://127.0.0.1:8080/wm/topology/route/00:00:00:00:00:00:0a:01/1/00:00:00:00:00:00:0a:04/1/json
+#
+
+## Global Var ##
+ControllerIP="127.0.0.1"
+ControllerPort=8080
+
+DEBUG=0
+pp = pprint.PrettyPrinter(indent=4)
+
+app = Flask(__name__)
+
+## Worker Functions ##
+def log_error(txt):
+  print '%s' % (txt)
+
+def debug(txt):
+  if DEBUG:
+    print '%s' % (txt)
+
+# @app.route("/wm/topology/route/<srcdpid>/<srcport>/<destdpid>/<destport>/json")
+def shortest_path(v1, p1, v2, p2):
+  try:
+    command = "curl -s http://%s:%s/wm/topology/route/%s/%s/%s/%s/json" % (ControllerIP, ControllerPort, v1, p1, v2, p2)
+    result = os.popen(command).read()
+    parsedResult = json.loads(result)
+  except:
+    log_error("Controller IF has issue")
+    exit(1)
+
+  debug("shortest_path %s" % command)
+  debug("parsed %s" % parsedResult)
+
+  for v in parsedResult:
+    dpid = v['switch'];
+    port = v['port'];
+    print "PathEntry: (%s, %s)" % (dpid, port)
+
+
+if __name__ == "__main__":
+  usage_msg = "Usage: %s <src-dpid> <src-port> <dest-dpid> <dest-port>" % (sys.argv[0])
+
+  # app.debug = False;
+
+  # Usage info
+  if len(sys.argv) > 1 and (sys.argv[1] == "-h" or sys.argv[1] == "--help"):
+    print(usage_msg)
+    exit(0)
+
+  # Check arguments
+  if len(sys.argv) < 5:
+    log_error(usage_msg)
+    exit(1)
+
+  # Do the work
+  shortest_path(sys.argv[1], sys.argv[2], sys.argv[3], sys.argv[4]);