ENH: Working prototype of add_to_canvas behavior for query_dict

@NSLS-II/development-team Here is a working prototype of the desired behavior in VisTrails when a user wants to add their scan to a VisTrails canvas. See `example_vistrails/add_to_canvas_brokerquery.vt`.  That .vt file currently requires that you be on one of the computers at CSX with the devel branch on metadataStore installed.  I will continue to update this as I make progress, but have a look.
it will once i can actually search on _id through the data broker. until then having the guaranteed unique search dict be {'_id': _id} doesn't work