Task to register help artefact with panopticon

Replaced rummager task with a no-op for now.
Fix layout of related box on help index page
Load help artefact on help index page
Update rummager:index task to call the panopticon one.

So that everything will continue to work until the deploy hooks have
been updated
Merge pull request #434 from alphagov/help_artefact

Register and use an artefact for the help index page.