Only index CIPs with live Organisations.

Add search_only method in Edition which is referenced by :only key in
searchable, and override in CIP to join on organisations with govuk_status: live
Fixes for CIP migration

* Use find_each for efficiency
* Fix creation of Worldwide CIPs
* Explicitly queue for indexing.
Use en dash in CIP search title.
CIP model unit tests working.

* Rename attributes where necessary.
* Remove validation tests for things we are no longer validating (unique CIP for
  type/organisation; and organisation required).
* Search index tests explicitly call update_in_search_index, since we no longer
  index on save.