Remove all use of "img" and "db" fields in views, in favor of ViewerRecords
Fix favorite creation to save fields appropriately as ObjectIds
Rename use of 'image_image_store' to 'image_store'
Remove unused Python imports
Merge branch 'view_schema_cleanup'

* view_schema_cleanup:
  Remove unused Python imports
  Rename use of 'image_image_store' to 'image_store'
  Fix favorite creation to save fields appropriately as ObjectIds
  Remove all use of "img" and "db" fields in views, in favor of ViewerRecords
  Session's view list RefItems should not require a database to be specified