Implement local government relevance filtering in NotQuiteAsFake
Add search_format_types to the editions searchable interface

This is an array of values that allows us to tag documents as their type and any grouped types that might cut across multiple classes (e.g. StatisticalDataSets and Publications with a PublicationType that is in PublicationType.statistical are both tagged in search_format_types with publicationesque-statistics).

Conflicts:

	app/models/case_study.rb
Editions can generate their own search_format_type programatically

Most instance methods use the class method and add it to the result from the superclasses.
Fill in the blanks in the rummager implementation of DocumentFilter

We make use of the search_format_types to do filtering instead of a combination of format and the various xxx_type fields.
format_types is search_format_types
Tidy up DocumentFilter::Rummager

Specificcally, most filter_xxx methods don't take args and we need to record the result of calling them and merging them in.
Make Rummager the default search backend

Pull in the advanced-search-for-whitehall branch of the gds-api-adaptors gem in order to use the new methods.

Notably all the values in the params have to be strings.  They can be arrays or hashes, but the values contained within must be strings.  It might make sense to push this down to gds-api-adaptors.
Cope with an empty result set from Rummager
Add search_format_types to the XXXFilterOptions

Use this to greatly simplify the code in DocumentFilter::Rummager for searching by announcement or publication type.
Send dates to rummager in a better format
Tidy up AnnoucementFilterOption
Construct paginated array using new total returned by Rummager
Add eager loading of result associations in DocumentFilter::Rummager
index world locations in rummager
Tidy up

remove ES doc filter
Use slugs instead of ids
remove unused searchable fields