Data Deletion and DB Cleanup

[Patrick de Perio]

Christopher Tunnell (from Gitter):
To make cleanup easier when things like that happen, maybe we should have an extra field for each data location called 'delete_me' that the local cax instance can pick up. It would then delete the local copy then remove the database entry. This would greatly simplify cleanup. Right now it requires ssh, then rm -Rf, then removing the entry manually from rundoc. A flag to stage something for deletion seems easier and also means that we can check that we still have other copies!