Sort unrated songs when requesting

This is how I do it in wormgas. Because the sorting procedure is so complex, I pull data from the database unsorted and process it with Python.

I wasn't 100% sure about the difference between `db.c.fetch_list` and `db.c.fetch_all`, so I hope I got it right.

I tested the SQL directly against the database so I know the query is good, but I have not tested the code.