Show stats nav and remove beta notices

A tabbed navigation allowing users to navigate to the
stats announcements index from the statistics page was
commented out as a feature-flag.

This reinstates it and removes the beta notices on the
stats announcements pages.

Also renames a couple of mis-named scss modules.
/government/statistics shows filtered index of statistics

Statistics are being extracted from the publications section of the site
to be displayed under /government/statistics. This commit creates a new
statistics controller.

It's more of a smoke-and-mirrors approach; The new StatisticsController
inherits from PublicationsController and gets most of it's functionality
from there.

Some thought was given into whether building a new provider in a similar
pattern to the stats announcements, but we decided that since gds hasn't
decided on what shape this kind of thing should be yet, it would be better
to take a less drastic approach for now.
Statistics show pages live at /gov/statistics/:slug

There wasn't much to do here as the new StatisticsController
already inherited everything it needed to show statistics pubs
from the publications controller.
Change the warning text on statistics announcements

Editors are posting the wrong documents as statistics announcements. This change is to the warning text on the Statistics Announcements page.
Merge pull request #1600 from alphagov/statistics-announcements-warning-text

Change the warning text on statistics announcements
Reduce sidekiq workers per box

This brings whitehall into line with the number of workers on other
apps. It also will help prevent us DDOS-ing transitioning servers during
importing of large numbers of documents/attachments
Merge pull request #1602 from alphagov/reduce-sidekiq-workers

Reduce sidekiq workers per box
Remove the remaining alternate top tasks

The last department are being migrated onto the new style services and
information links. This feature is no longer needed so remove it and all
the related styles to go along with it.
Merge pull request #1603 from alphagov/remove-alt-top-tasks

Remove the remaining alternate top tasks
Use SASS style imports for admin stylesheets
Don't duplicate admin styles

* Remove extra admin stylesheet include
* Update conditional stylesheets to start with admin.css rather than
base.css, so that all styles for bootstrap, jquery-ui etc are included
Don't overwrite default behaviour of span2 class

* Styles made all span2 classes expand to 100% at small widths
* Instead, do this explicitly with a new class

(Bootstrap 3 has proper hooks for doing this)
Remove unused nav-header overrides

* There are no nav-headers being used in the admin app anywhere
Configure Whitehall search client

* Adds unified_search_client
Adds ServicesAndInformation resource

* Adds route, controller and views
Adds ServicesAndInformationCollection

* Adds ServicesAndInformationFinder to wrap Rummager call
* Adds ServicesAndInformationParser to extract required info from
  Rummager response
Filter organisations needs slug, not name

Look up responses by string rather than symbol
Updates gds-api-adapters to version 12.1.0

* Update necessary to use Rummager test helpers

* Changes tests to use Rummager test helpers in gds_api_adapters gem
Style services and information page
Actions PR comments

* Removes ServicesAndInformation#to_partial_path since it is not needed
* Corrects services and information route to comply with standard naming
* Moves 'full list of topics' link inside org Services and guidance
  conditional
* Corrects test to ensure it is using an org with featured services and
  guidance