pathfinder returned format

[gloriachin]

encode the pathfinder returned objects into one dictionary or object.

[yjzhang]

TODO: the format returned by TCT.pathfinder should be similar to the format returned by https://aragorn.test.transltr.io/aragorn/docs#/ARAGORN/sync_query_handler_query_post - we can leave out the node attributes, but we should include the edge attributes (sentences/publications supporting the edge).

[yjzhang]

For the function TCT.Path_finder, we should return a single output result rather than a long tuple of things.