More informative responses

Currently after any REST API call, I get a message like the following:
```
DEBUG: "PUT /api/v1/graphs/22934 HTTP/1.1" 200 None
```
It would be much more helpful if we had a message like "Success: graph posted" or "Graph shared successfully" or "no layout with name 'layout1' for graph 'graph1' and user 'user1' was found" or whatever the REST API call and result was