Re-registers unpublished/archived/deleted editions

Editions which have been archived or unpublished in Whitehall don't have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.
@tekin, after some investigation and clarification on the acceptance criteria that leads to this Rake task, we are to retrieve all "unpublished" editions - ie. editions that have an `Unpublishing` associated.