R#: Delete member.

Remove `ICalendarItemRepository` field from `BannerModelQuery`.
R#: Delete argument.

Remove the `ICalendarItemRepository` argument from the constructor on
`BannerModelQuery`.
R#: Check argument for null.

Add a null check for `IConferenceLoader`. Previously there was a
duplicated check for null on `ICalendarItemRepository` instead.
Add new query object for a single calendar item.

This is an interesting second query object, because it doesn't have the
same interface as the first: it returns a scalar value and accepts a
parameter, rather than returning a collection and accepting no parameters.
Add query object to `DataProvider`.

Add temporary constructor overload so usages of the existing constructor
continue to work.
Update `DataProviderFactory` with the new query.

Use the new constructor overload in `DataProviderFactory` to pass the new
query object in.
Make `DataProvider` use the new query object.

It seems there aren't any tests covering this class at all.
R#: Delete field.

Remove the now-unused `CalendarItemRepository` field from `DataProvider`.
R#: Delete constructor parameter.

Remove the now-redundant `CalendarItemRepository` constructor parameter from `DataProvider`.
R#: Delete temporary constructor overload.

The overload is no longer in use, so it can be removed.
Add temporary constructor overload.

Take the new query object as a constructor parameter on
`TimelineController` and introduce a constructor overload to allow
existing code to continue working.
Replace usages of `CalendarItemRepository`.

Update `TimelineController` to use the new
`GetCalendarItemFromCalendarEntryTypeQuery` object rather than the
`CalendarItemRepository`.
R#: Delete member.

Delete the now-unused `GetFromType()` method from
`ICalendarItemRepository` and its implementation.
R#: Delete member.

Delete the now-unused `ICalendarItemRepository` field on
`TimelineController`.
R#: Delete member.

Remove the now-unused overloaded constructor of `TimelineController`.
R#: Delete argument.

Remove the `ICalendarItemRepository` argument from the
`TimelineController` constructor.
R#: Delete member.

Delete now-unused `ICalendarItemRepository` field from the tests for
`ConferenceBuilder`.
R#: Delete class.

Delete `CalendarItemRepository` which is no longer used anywhere.
R#: Delete interface.

`ICalendarItemRepository` is no longer in use anywhere, so it can be
removed.
R#: Rename file.