Untangle Publishing API from Panopticon registration

These are not the same things so we shouldn't use the same decorator class,
especially given Panopticon will eventually be retired.
PublishingApiPresenters::Organisation for consistency

Mirrors how we are doing adding editions to content store with Publishing API
Rename publishing API workers

Neither "register" nor "artefact" are terms that are appropriate for the new
publishing API. This renames the workers to better reflect what they are for.

Note that the old files are left in place with the constants set as temporary
aliases of the new classes. This is so that any jobs already queued against the
old worker classes can still be processed. This will need to be cleaned up in a
future commit.
Remove unnecessary queues

We don't set different priorities for these jobs so there is little point in
having a separate queue for them.
Add FIXME note for later cleanup
Merge pull request #1794 from alphagov/publishing-api-presentation

Clean up code that is publishing to Publishing API
Move table’s inline styles to stylesheet
Move table announcement styles to stylesheet
Correct alignment of publication checkbox

* Reset generic filter styles applied to form elements when in a
checkbox container
Add a remove margins helper class
Make publication filter more readable

* Refer to the announcement not having a linked publication, rather
than the release — the release is the publication
Re-order release date options

* Next 2 weeks is still in the future
Improve language around statistics announcements

Making the numbering friendlier, and with correct pluralisation, plus using more
appropriate descriptions for past, future and all.
Merge pull request #1807 from alphagov/improve-stats-announcement-filtering

Improve stats announcement filtering
Extract & reuse method to return possessive form

Extends the base String class to return the possessive form of a string and
updates the admin editions filter to use the correct form.