workflows: sphinx documentation and more

• Adds sphinx documentation syntax to functions in the module.

• Fixes a problem with duplication of logger, the logger was a singleton but not the handlers which were accumulated each time we were continuing a workflow, producing database burst.

• Deletes some dead code.

• Fixes a mistake which was due to limitations in extra_data access.

Reviewed-by: Jan Aage Lavik <jan.age.lavik@cern.ch>
Signed-off-by: Guillaume Lastecoueres <guillaume.lastecoueres@techie.com>