In Features & Steps: country => world_location

This commit breaks things as no code other than steps has been updated.
At the model level Country => WorldLocation

No types yet and join objects still talk about country.
In models EditionCountry => EditionWorldLocations
WorldLocations have a world_location_type

Following the pattern for Publication#publication_type and
Speech#speech_type we're using a AR-esque, but not DB persisted
WorldLocationType object.
Rename remaining associations and methods for country => world_location

We haven't replaced any usages of these that exist outside app/models.
We're getting to that.
In lib/whitehall/uploaders country => world locations

Renamed finder and the attributes it is used to populate.
The public CountriesController => WorldLocationsController (incl. views)

NOTE: I've tried to remove country/countries classes and replace with
world-location or world-locations classes where I can, but Rails
(specifically content_tag_for et al) will generate world_location instead
of world-location.  So there will be some discrepancy, but I assume we had
that already on other CamelCase named models.

I've also not updated the CSS to reflect the class changes. Yet.
Fix references to can_be_associated_with_countries?
Fix references to country_path and countries_path
Fix references to list_of_links_to_countries_once_world_goes_live
HTML attrs prefer to be wrapped in ""
Move list_of_links_to_statistical_data_sets to DocumentHelper

Might not be the right place for it, but it certainly doesn't belong in
CountryHelper.
Remove unused class on body div for world_locations/index
Remove unused options params when rendering 'shared/hero_rotator'

Also convert to "new" style of partial rendering.
Admin CountriesController => WorldLocationsController (incl. views)
Admin EditionsCountriesController => EditionWorldLocationsController
Rename & fix functional test macros that deal with country behaviour
Fix _country_fields partial in light of Country => WorldLocation

Also renamed it to _world_location_fields.
PoliciesController exposes world_locations not countries
Rename Edition::Countries to Edition::WorldLocations