Stale data deletion

[AlexandreHutton]

Users are identified by their session cookie. In the event that their cookies are cleared, they lose access to their results and the data would sit on the server indefinitely.

To fix:

• Every day, check the DB, identify old data and delete it.
• If a user returns with the session cookie, we should modify it to drop data that is not found.
• Add "last accessed" column to results. Update on fetch.