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>