New requirement for implementations of IDocumentMetadataSource plugin

If you write your own implementation of the IDocumentMetadataSource plugin interface, there is a required change during upgrade to version 9.0.

After retrieving a document, call the new setRetrievedFromIDMS method on the Document entity instance. The method sets doc.PersistenceRequired to false and marks the document as coming from the IDocumentMetadataSource plugin.