Make org slug changer add CIP redirects

These live under the org's namespace, and therefore need redirects put
in place.
Add extra log output with redirect info.

In order to help with adding the redirects to router-data this now spits
out the necessary CSV lines at the end of the run.
Merge pull request #1881 from alphagov/org_slug_changer_cip_handling

Make organisation slug changer add CIP redirects
Check for markup equivalence, not string match

This gets around the issue of different versions of libxml generating subtly
different whitespace/newline output.
Merge pull request #1899 from alphagov/make-tests-more-robust

Check for markup equivalence, not string match
Add more links to services and information pages

This commit turns on the link for the HMRC services and information
page: this is a time-critical change which needs to go out on Wednesday
10th December - and HMRC will need to be informed so that they can
remove a duplicate link from their organisation page when it has been
deployed.

It also adds links for several other organisations (DfE, HS2, DVSA);
these ones are not time-critical.
More unpublishing repairs

This converts a bunch of auto-redirecting unpublishings so that they do not
automatically redirect as they are not on GOV.UK. Instead, a splash page will be
shown. This is because the Publishing 2.0 stack does not support non-GOVUK
redirects at present, and whitehall Unpublishings are not valid without a GOVUK
alternative URL.
Merge pull request #1900 from alphagov/services-info-pages-for-hmrc-and-others

Add more links to services and information pages
Merge pull request #1901 from alphagov/moah-fix-unpublishings

More unpublishing repairs
Correct `dependent: :destroy` for CIPs

www.agileplannerapp.com/boards/173808/cards/8853

there's a `dependent: destroy` on organisations to destroy associated
corporate information pages when the organisation is deleted. in spite
of that few orphaned CIPs exist: 336462, 336498, 363483.

there are changes in 2 places to fix this issue:

1. `dependent: :destroy` on `corporate_information_pages` association
   only destroys the record in the join table and not the corporate
   information page edition. so the fix is to have an explicit
   `before_destroy` to clean corporate information editions
   and documents.

2. callbacks are invoked in the order in which they're declared.
   if the `before_destroy` to destroy corporate information gets
   registered before the `:edition_organisation, dependent: :destroy`
   this will work. else, when the callback tries to destroy related
   corporate information pages it won't be able to fetch the related
   corporate information editions because the linking record is gone.