Refactor poll_profiles

- Create fetcher classes for fetching records via an OAI feed,
  an absolute URL, and local XML files
- Split ingestion process into scripts create_ingestion_document,
  fetch_records, enrich_records, save_records, and
  remove_deleted_records
- Update profiles to work with split ingestion logic
- Clean up modules to include only useful logger messages
Add script to update legacy ingestion documents
Add hathi_identify_object module

- Add unit tests for hathi_identify_object module
- Add thumbnail pipeline to Hathi profile
- Update poll_storage to work with split ingestion process
Merge branch 'release-v7.0'