Add RT film alias

Set an alias of namespace rt:filmid to the RT film ID.
Also fix a bug that meant multiple versions were being
created.
Merge pull request #482 from atlasapi/radiotimes-set-alias

Add RT film alias
Link clips based on clipOf since the URI no longer
contains the episode URI
Update C4 clip embed code
Merge pull request #483 from atlasapi/inline-clip-extraction

Inline clip extraction
Iterate over known channel aliases for redux latest
ingest
Merge pull request #484 from atlasapi/redux-latest-for-channels

Iterate over known channel aliases for redux latest ingest
Purge content

Add controller to allow purging of content for
lyrebird youtube publisher.
Merge pull request #485 from atlasapi/purge-content

Purge content
Don't query Nitro for all availabilities

If Nitro fails to fetch programmes or clips, don't
attempt an availability query without the context
of a programme. This is rather a large query...
Output parent channel on items

Parent channels are generally useful for branding
purposes. Therefore we'll output if channel information
is requested with the CHANNEL_SUMMARY annotation.

We are also overriding the images provided for parent
channels because we don't yet receive images on parent
channels (a.k.a. stations) from PA, currently our only
source of channels.
Merge pull request #486 from atlasapi/parent-channel-output

Output parent channel on items
Change parent channel override images
Require genuine SubstitutionTableNumberCodec in test
use kafka