Rac-es

Adds
- Adds category field to Document definitions.

Adds
- Adds `group` field to Collection, Object, Term and Agent, removes `top_collection`
- Updates fixtures
- Streamlines URI handling in tests

Adds
- Adds additional fields needed for search:
- Added a `top_collection` field, which will help us group results by collection.
- Added a `formats` field so we can facet on that.
- Added an `online` boolean so we can filter by things that are online or not
- Separates the `agents` key into `people`, `organizations` and `families` (and added these to `agent` objects as well) so we can facet on particular kinds of agents rather than all of them.

Adds
Removes creation of `source_identifier` fields.

Fixes
Adds a `uri` field to BaseDescriptionComponent.

Fixes
Removes unnecessary arguments from `bulk_action` method