workflows: Holding Pen improvement

• Provides a default label for an object in the Holding Pen main table in cases where there is no title extracted from the data.

• Adds a convenience button to restart workflow on the current task if there is an error (useful while fixing a problem).

• Improves the base_details.html template to make it easier to customize.

• Shows only the object with "Need action" by default.

• Handles better Unicode characters when searching in Holding Pen.

• Handles the case when the workflow name is None.

• Renames variables and functions for clarity.

• Uses .get_or_404 instead of just .get when looking up BibWorkflowObject in the Holding Pen blueprint to avoid exceptions should an object ID be non-existent.

Reviewed-by: Jiri Kuncar <jiri.kuncar@cern.ch>
Signed-off-by: Jan Aage Lavik <jan.age.lavik@cern.ch>