Transfer detail view: enable DC metadata

This enables Dublin Core metadata to be entered in a transfer, as well
as in ingest. Later commits will ensure this is persisted into ingest
as expected.

refs #6217
Add saveDublinCore microservice

This microservice serializes DC metadata to disk at the end of a
transfer, ensuring it's saved when the database is no longer present
(for instance, during SIP arrange).

refs #6217
Add loadDublinCore microservice

This microservice loads DC metadata from disk and populates the DB at
the beginning of ingest. This allows DC metadata entered during the
transfer to be used the same way as DC metadata entered in ingest.
Since this happens at the beginning of ingest, it also ensures that
it continues to be editable via the UI from very early on in ingest.

refs #6217
Transfer DC metadata form: Remove unnecessary dropdown

refs #6480
createSIPfromTransferObjects: copy JSON metadata

refs #6217