Changed OAIVerbsFetcher.fetch_sets() dict key

Changed dict key "description" to "setDescription" to match what
comes from the OAI endpoint.
Add default rights statement to IA records - fixes #6499
Merge branch '6499-ia-rights-default' into develop
Fix 7122

- If collection list has only one dictionary, set the record's
  sourceResource.collection to that one dictionary
Update DC_DATA_PROVIDER
Merge branch 'develop' of https://github.com/dpla/ingestion into type-field-by-format