Refactor projects to have unique REST-appropriate identifiers

[nickavv]

Since the frontend is now going to interact with the backend in a RESTful way, it would be handy for everything to be addressed by simple unique identifiers (UUIDs probably).

Currently Projects is the only front-facing model I think. This change will probably involve changing how they are keyed in the datastore, and then changing specifically the Delete Project API's path to /projects/{id} instead of just /projects, removing the DeleteProjectRequest class (moving the "also delete from disk" boolean into a query parameter), and then changing the frontend to send the DELETE request that way instead of the current way.