Don't play songs reported as copyright infringement on /api/play

[tbinetruy]

Songs that have been copyright infringed shouldn't be playing on /api/play and shouldn't be playable from anywhere on the website until it has been reviewed by the MASAS team.

Therefore, what is needed is a field similar to 'deleted' on /api/songs/song_id but that says 'under copyright review'. The admins can then either remove the song from the servers if it is reviewed as copyright infringement or unreview it if it doesn't infringe copyright.