Re-registers unpublished/archived/deleted editions

Editions which have been archived or unpublished in Whitehall don't have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.
OK, but be careful with that. An edition with an `Unpublishing` may still have been superseded by another edition that is not in the same state (i.e. the newer edition is "published") and so registering the superseded edition that has the `Unpublishing` will send it to Panopticon as "archived" whilst the latest version is actually "published.