Fixes in EAD bioghist import/export, refs #7124

  - 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

Squashed commit of the following:

commit ec49f3fbef524dd534249421ae1661ee9ad49ba4
Author: José Raddaoui Marín <raddaouimarin@gmail.com>
Date:   Fri Dec 12 23:58:27 2014 +0100

    Add @param to function comments

commit 907d5d20cc22177e424f1db8c7116812f3a42651
Author: José Raddaoui Marín <raddaouimarin@gmail.com>
Date:   Fri Dec 12 00:12:33 2014 +0100

    Fixes in EAD bioghist import/export, refs #7124

    - 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

    See #7124, updates #7 and #8