Closes: #180

This reverts commit 3c611393.

The filter annotation for ordering by show ownership introduced
a join that caused some results to appear more than once.

The dashboard will need to implement a paginated list of shows
that should be searchable.

The dashboard must be able to sort shows.

In aa7e7f41 filters were renamed
to a camelCase scheme. This is actually wrong, because the filter
names are already transformed to snake_case when the are applied
to the FilterSet.

The nested timeslot routes allowed us to filter the timeslots by show
and schedule. We’ve deprecated nested endpoints with the alpha.2
release, but still need the actual filtering logic.

We need the search filter to implement a user complete field in the
dashboard.

This is the counterpart to the
requires_express_permission_for_publication field of the License model.

The Timeslot no longer has a show attribute. It is exposed through timeslot.schedule.show instead.

add `needs_author`, `requires_express_permission_for_publication` and `url`

update LicenseSerializer and license fixture

- replace LicenseType with License model, update fixture, serializers, views, and urls

Closes: #167

Closes: #171