BibEditMulti: delete unsaved subfields when deleting a field
BibEditMulti: delete unsaved subfields when deleting a field

* While deleting a field from the action interface, delete
  all subfields related to the field and not yet saved
  (closes #444)

tiborsimko/invenio,inveniosoftware/invenio,inveniosoftware/invenio,tiborsimko/invenio