Update EAD mappings

* Find `<origination>` values when `<origination>` is not parented inside the `<did>` element
* Map `<publicationstmt><date>` to revisionHistory. This field describes the date of publication of the *description*, but it was being mapped to a field that actually refers to the content being described.

The latter change orphaned the `setPublicationDate` method on `QubitInformationObject`, so it was removed.