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 branch 'parent-channel-output' into stage

Conflicts:
	src/main/java/org/atlasapi/system/ContentPurgeWebModule.java