Add rake task to republish all related links
Add rake task to republish all related links

Since https://github.com/alphagov/panopticon/pull/396 we're sending the
related artefacts in the links hash to the publishing-api. This commit
adds a rake task that republishes all the related links, so that the
publishing-api is up to date.

alphagov/panopticon,alphagov/panopticon,alphagov/panopticon,alphagov/panopticon