scripts: extends fix_marc_record script

* Adds an option to fix a record with a specific record
  if from a given Invenio site.

* Improves the author names fixes.

Signed-off-by: Georgios Papoutsakis <georgios.papoutsakis@cern.ch>
Merge pull request #85 from GiorgosPa/scripts

scripts: extends fix_marc_record script