workflows: holdingpen improvement

* Removes selection of row on link click.

* Changes the way of update data in approval widget.

* Changes the way of handling widget in pages.

* Changes the way of managing tags.

* Adds retrocompatibility for _widget field in extra_data.

* Simplifies the handling of informations in the http
  request.

* Adds new way to extract data from bwOject.

Signed-off-by: Guillaume Lastecoueres <guillaume.lastecoueres@cern.ch>
workflows: str() addition to calls

* Fixes an issue in the MARCXML tasks that caused legacy
  create_record to fail when a string is passed as unicode.

Signed-off-by: Jan Aage Lavik <jan.age.lavik@cern.ch>
workflows: Holding Pen display changes

* Replaces the 'source' column with a more useful
  'identifier' column in the main HP display.

* Tries to factor out some of the data extraction
  happening when displaying object data in Holding Pen.
  Will be revisited in the near future.

Signed-off-by: Jan Aage Lavik <jan.age.lavik@cern.ch>