Link to the first mainstream spelling suggestion

This is (probably) firing a duplicate search query, I'll refactor that shortly.

CSS, markup and accessibility advice courtesy of @markhurrell and
@workwithgreat.
Hide spelling suggestion with feature flag

The spelling suggestion currently generates rude words, so we need to consider
how to deal with that before we can make this public.
Avoid duplicate mainstream request

Caching may have prevented an actual duplicate request, but you'd have to know
detail about gds-api-adapters to even guess that. Anyway, the cache is
generally disabled in development.

Additionally make it backwards compatible with Rummager before spelling
suggestions were added.
Retain spelling suggestion feature flag on search
Retain tab and spelling feature flag on suggestion
Fix brittle test broken by last commit
Remove references to business_proposition flag

This flag isn't used for anything any more and we want to use other mechanisms
for identifying content relevant to businesses.
Merge branch 'master' into spelling_suggestions

Conflicts:
	app/controllers/search_controller.rb
Don't list multiple locations in search results.

Certain publications are associated with a large number of world locations,
and so show up with a great long list in the search results. This is quite
confusing, so we just say "multiple locations" and let people follow through
to the publication if they want the whole list.

This was the initial behaviour, but was changed (possibly inadvertently) in
commit e0a7a6150076ad9de0b9cb59e568535fff7dc629.
Merge pull request #365 from alphagov/fix-world-locations

Don't list multiple locations in search results
hgroup got removed from the draft spec. replaced all instances with divs for now.
Remove panopticon registration task.

This was only for campaigns, and these should not be registered, as
they're not wanted in search.

This task was not being run on deploy (or at any other time), but its
presence provides confusion, and could lead to mistakes.
Bump slimmer to 3.17.0

To enable us to fix the breadcrumb markup
Remove registerable_campaign as it's no longer needed
Remove references to the images, since we'd rather everyone use link text
Remove logos
Merge remote-tracking branch 'origin/crown-usage'
Remove G8 summit promo from gov.uk homepage

Reverts 875b006f. See https://www.pivotaltracker.com/s/projects/367813
Fix intermittent undefined constant in Search

From time to time, in development, Rails' autoload would not be able to find
the definition of the GovernmentResult constant. This was because it wasn't in
a file that matched it's name.
Identify government results

Makes it easier to pick out government results in the top 3 results.