Properly follow the purge/decommission behaviors when removing a Hydrus object

[blalbrit]

In the current state, deleting an object from Hydrus also deletes it entirely from DOR. If the object has already been accessioned, this process leaves an orphan object in the preservation core and, if any workflows were active when the object was deleted, wreaks havoc on the workflow archiver (which repeatedly times out trying to archive table rows for an object that no longer exists).

The desired behavior is as follows:

• if the object is registered only (that is, it has not been "published" in Hydrus), it should be purged (it can be fully deleted from DOR as happens currently)
• if the object has ever been "published" (ie. it has been accessioned and preserved at least once), it should be decommissioned

An overview of current-state decommissioning is here: https://consul.stanford.edu/display/chimera/Decommissioning+DOR+objects

For reference, desired state in SDR3 is here [draft]: https://docs.google.com/document/d/1zBr93MRg8wJUE7QMpOkWB8R6XWWfEkiUUz_o2T6FIC4/edit

Don't hesitate to ping me and @hannahfrost for additional clarification or details