Explanation: The upgrade to Liquidsoap 2.0 now means that Liquidsoap itself can hold more than one song in its upcoming queue, which allows us to make functionality like "skip song" work as expected for the first time, but also meant that our previous methods of tracking what songs were and weren't queued didn't work well at all. This overhauls the queue builder by adding a new "is_played" status to each queue entry and treating the entire "unplayed" queue (whether sent to the AutoDJ or not) as the "upcoming" queue, fixing a number of issues.
This migration adds "Storage Locations", managed via a new System Administration panel, that can hold Station Media data, live broadcast recordings, and backups. These storage locations can be local (as they are by default) or remote via any S3-compatible service.
* Create new backup and restore commands allowing live backups.
* Switch migrate script to use new backup method.
* Avoid loading fixtures, ensure directories exist when restarting stations.
* Include album art in media backup.
* First portion of automated backup management code.
* Further backup page work; add download/delete functionality.
* Implement automatic backups and "manual run" page.
* Switch automatic backup filename to match text.
* Add new locales.
* Add restore instructions and ability to view latest backup log.