Don't use username when selecting sounds and packs from the database

Since we have the sound/pack id there's not really any reason to also
limit by the username. This speeds the query up a little bit (sometimes
not by much since the username is in an index anyway)
In order to keep the same behaviour as before (404 if the username
is wrong) check the username of the sound after it's been retrieved
Merge pull request #582 from MTG/sound_speed

Don't use username when selecting sounds and packs from the database