These filters now support datetimes as well as dates and their naming
now reflects what they are querying.

The default values break some valid use cases and there’s no real value
in applying them by default.

refs #189

Closes: #185

Closes: #178

Closes: 183

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.