Update case_study.json schema with new links
Add policies & world priorities to case study format
Republish all publicly visible case studies

This is to add related policies and worldwide priorities to their links hashes.
Remove indirection
Merge pull request #1892 from alphagov/meta-data-for-case-study-format

Meta data for case study format
Render archiving explanations as govspeak.
Merge pull request #1895 from alphagov/govspeak-in-archiving-explanations

Render archiving explanations as govspeak.
Fix redirects on existing Unpublishings.
Tweak data migration logging output
Parameterise whitehall public root

This ensures the data migration does the right thing, regardless of the
environment it is run in.
Repair alternative urls with stray whitespace

At least 4 Unpublishings have alternative urls with a stray whitespace at the
beginning. This will remove any stray whitespace.
Merge pull request #1894 from alphagov/fix-unpublishings

Fix redirects on existing Unpublishings.
Add unpublishing presenter.
Use Unpublishing format for unpublished editions.
Send unpublishing on unpublish action.
Data migration to push all unpublished editions.

Modifies PublishingApiRepublisher not to skip non-published editions if
they have an unpublishing.
Move publishable? logic to PublishingApi.
Add schema for unpublishing, validate in test.
Add redirect presenter.

Includes JSON schema validation.
Fixes to unpublishing presenter

Explanation renders as govspeak, and empty alternative_url should be
empty string not nil.