Re-registers unpublished/archived/deleted editions

Editions which have been archived or unpublished in Whitehall don't have
their state updated in Panopticon.

Story: https://www.pivotaltracker.com/story/show/69528904

This adds the "unpublish" and "archive" verbs to the Panopticon
Registrar service listener and sets the adequate state on the
RegisterableEdition object sent to Panopticon.

This solution also requires updating `edition_test#should_remove_published_edition_from_search_index`
since this now triggers an external request.
These tests would be better with a common `setup` that creates the editions and does the necessary stubbing to reduce noise and make them more readable. Also, it would be better if the use of the unpublisher better reflected it's real world usage by handing in the `:unpublishing` parameters as an option, rather than manually creating them first. See https://github.com/alphagov/whitehall/blob/master/app/controllers/admin/edition_workflow_controller.rb#L156 for an example of usage.