Add GOVSPEAK_DEV environment variable to use local govspeak

When working with govspeak it's nice to be able to boot whitehall using
a local copy.
Migration to update LegislativeList syntax

Versuion 3.0 of govspeak introduces a breaking change for legislative
lists, requiring a closing tag.

This migration adds a closing tag to any existing uses of
`$LegislativeList` in HTML attachment bodies in the place that the list
end would have previously been inferred.

This is done as a migration rather than a data migration to try to
ensure a minimum length of time that things look broken. It should only
be broken for the time it takes for unicorn to finish restarting.
Add CSS for legislative lists
Add extra style override for legislative list

We want the ol.legislative-list style to apply both in the very specific
html attachment show case as well as in the generic "this is govspeak"
case therefore override it in both places.
Merge pull request #1659 from alphagov/update_legislative_list_syntax

Bump govspeak to 3.0 for new LegislativeList syntax
Add GDS_ADMIN permission.
Require GDS Admin permission for new/create orgs.
Tests for GDS Admin permissions.
Stop incorrect date initialisation at month end

Bug manifested as a failing test on Aug 29, the tests use February as
an example. The JavaScript was creating a date, using today, then going
through and setting each of the properties, eg year, month etc. On
August 29, setting the month to February would try and create a date
“February 29” (non-leap year) which is not a valid date, so JavaScript
switches to March 1st.

* Avoid bug by creating variables from each date input then creating a
date all at once
Merge pull request #1691 from alphagov/fix-stats-js-date

Stop incorrect date initialisation at month end
Bump slimmer to 4.3.1 for new slimmer header
Add filters to searches on land registry pages

When a search is performed on content which is owned by the Land
Registry, scope the search results to contain only land registry
content.  This is for https://www.pivotaltracker.com/story/show/77617490

Since the Land Registry transitioned, we've seen a sharp and significant
increase in the number of search results which get no result clicks.
Also, analytics shows that lots of fairly generic searches are being
performed from land-registry pages (eg, for terms such as "portal" and
"forms").  Our hypothesis is that these are searches from people who
have been redirected from the old site, and that these searches have a
high expectation that searches will be across Land Registry content.

We want to deploy a change now to filter the results accordingly.  The
results page will open with the "Organisations" filter box expanded, and
the "land-registry" organisation selected (and at the top of the list of
organisations in the filter box).  We'll then track the analytics to see
if this scope works well in this case, with a view to scoping or biasing
the search results from more organisation pages in future.
Remove warning message.
Unscope SpecialistSector relation to Edition 

Each SpecialistSector belongs to an edition. However, if the edition is 
deleted, requesting the relation returns nil as the default scope for 
the Edition model is to exclude deleted editions.

By overriding the relation to be unscoped, we can still perform 
operations on Editions related to SpecialistSectors regardless of their 
state.

This is based on prior art found in 
https://github.com/alphagov/whitehall/blob/ec83c2ea/app/models/classification_membership.rb#L25
Merge pull request #1689 from alphagov/scope-land-registry-searches

Add filters to searches on land registry pages
Merge pull request #1690 from alphagov/limit_organisation_creation

Limit organisation creation
Remove stray ' from "its" in a test
Merge pull request #1692 from alphagov/specialist-sector-relates-to-unscoped-edition

Unscope SpecialistSector relation to Edition
Merge pull request #1693 from alphagov/stray-apostrophe

Remove stray ' from "its" in a test