Get md5-hashing/duplicates working

Biblio hashing/duplicate checks have been temporarily commented out in biblio_save() for the sake of developer sanity.
We need to un-comment this code and make sure that we can check for duplicate Biblio entities properly, and add the same functionality to the Contributor entity.
I'm also not sure if the biblio_md5 field is something that should be stored in a Drupal field, or in the biblio table in the db.