Fixes in EAD bioghist import/export, refs #7124 (updates #7 and #8)

- Don't add empty bioghist elements in EAD export
- Don't create new 'Untitled' actors if bioghist value match
  the history value of the creator in the same position
- Improve comments showing different options on import
Yes, we're checking the actor name/repository in setActorByName, wich is called before the actors are added to the information object events. And the history is being checked in those conditions.