OAIHarvest: move to workflows

• Changes OAI Harvest daemon logic to use the new workflows module, with many changes overall.

• Refactors DB-layer for oaiharvest part. Uses the new sqlalchemy models.

• Changes OaiHARVEST table schema to add workflow options and removes frequency parameter. BibSched is the master of task frequency.

• Allows new CLI parameters --workflow or -r/--repository, --workflow or just only -r/--repository.

• Adds support to harvest with all combinations. It means one repository or one workflow, one repository N workflows N repositories one workflow or N repositories N workflows.

• Optimized request in daemon to mimize the number of workflows to start to complete the work asked.

• Improves task_run with better error reporting.

• Cleans the code of several functions, simplifies the harvesting a bit. Changes the way the updating of the last_time update.

• Updates OaiHarvest model in oaiharvester.

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