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
Adds publication path for services and info
Removes link to full list of topics

* Removing the link will allow us to deploy the services and information
  page without there being an way in the UI to access it.

* Changes features to reflect removing the link

* Clarifies feature scenario

* Changes ServicesAndInformationParser:
  make more use of methods available on GdsApi::Response
  assign subsector_link in #parsed_content to :link instead of :slug

* Changes ServicesAndInformationParserTest to check that all necessary
  keys are present in the parsed content instead of relying on checking
  explicit values returned by the rummager test helpers

* Changes link text on services and information collection group

* Changes route not to use "and"
Changes services and info finder query

* Adds "count: 0" to search query to optimize rummager search
Merge pull request #1601 from alphagov/build-search-and-information-pages

Build search and information pages