Make route helpers work with Worldwide CIPs.

Undo some of the previous changes to the helper and determine the route name
dependent on whether the CIP is associated with an Organisation or a
WorldwideOrganisation.

Also remove duplicated logic in document_path and make that call document_url
with routing_type: path.
Attachment and translation fixes for CIP migration

* Create new Attachment instances rather than converting old ones to make it
easier to roll back. Keep old AttachmentData.
* Don't set irrelevant lead organisation attributes.
* Style fix on translation logic.
* Override summary_required on model and don't set empty summaries in migration.
Search indexing for CIPs.

Make title reference in Edition point to overridable search_title method, and
override in CIP to return title_prefix_organisation_name.

Add display_type override in CIP.

Remove now-unused methods in CIP.
Removed commented and unused code in CIP.
Remove redundant workaround in CIP controller.