Feature/13569

Added views/graph.py code to qwery GWM models,  to generate required strings representing Javascript obects that will be useful to the client side scripts (to be added subsequently)
Added template file for rendering valid Javascript with the objects created previously.

Created a URLConf mapping from:
/graph?cluster=(slug) ------>  ClusterGraphView class
(This would be updated to pass the cluster in the URL itself, #todo)