Auto-archive jobs

[perry-mitchell]

Create a helper that automatically archives job trees that have succeeded over a month ago (or something to that effect).

[perry-mitchell]

Perhaps successful jobs could be archived after 1 month, and failed after 3 months? When archiving the entire tree should be looked at. If any are failed then 3 months, if any all are successful then 1 month, if any other state then archiving should skip that tree entirely.