add plugin to reingest recordings where the ingest has failed.

this is pretty simple but it seems to work nicely.

every `check_after` seconds (roughly, the plugin is only called when the `galicaster-notify-timer-short` event fires but this is not really a time sensitive thing) the repo is checked for failed ingests. if a failed ingest is found, it is added to the queue for re-ingesting.galicaster-notify-timer-short