workflows: Holding Pen tags and pagination

• Also adds Holding Pen main table pagination on top of the table in addition to the bottom one.

• Amends Holding Pen main table to properly show all records when all tags are removed.

• Fixes a problem with Holding Pen main table display when sessions are cleared.

• Changes the methods get_description, get_title and formatter to static and BibWorkflowObject argument names.

• Adds WorkflowBase inheritance in marcxml_workflow and sample_workflow.

• PEP8 fixes.

Co-authored-by: Jan Aage Lavik <jan.age.lavik@cern.ch>
Signed-off-by: Georgios Papoutsakis <georgios.papoutsakis@cern.ch>