Expose business support facets in response
Order results by priority and then title.

This emulates imminence ordering, business support results currently
preserve imminence ordering despite the order of results from the content api.
This ordering will become relevant once client apps (business-support-api)
switch to using contentapi for all results.
Tidy up elongated statement into readable code
Merge pull request #162 from alphagov/expose_business_support_facet_values

Expose business support facet values