Date Withdrawn and Retirement/Tombstone record

[wfyson]

The DataCite metadata should be updated with a Withdrawn date when an item is retired/removed, and the DataCite records, used to generate the tombstone pages, should be fleshed out with a reason and date withdrawn field.

"The metadata schema lists a “dateType”, “Withdrawn” as an option. It seems like this should also be updated when the retire button is pressed in order to correctly reflect what happened. It also seems like this, and the retirement reason, should live in the tombstone record."