Improve display/explanation of item provenence

[mikesname]

We need an integrated view of the "provenance" of an item which combines its "pre-EHRI" history with its post-EHRI history. We need to figure out the best way to infer the pre-EHRI history from a given item. e.g.

• Data from USHMM
• Converted by EHRI
• Imported by Ben

On the backend side we need to capture pre-import history with maintenanceEvents.

[mikesname]

• Add parent items down the RHS sidebar, beneath the repository. Preferably with some kind of view that suggests "parentage"?