Add .current and #english? methods to Locale
Elastic search use isn't controlled by this parameter.
Make all document list filters optional.

The non-english version of this form will initially only show
world location.  PErsonally I'm not a big fan of the 'if defined?'
pattern but I've followed existing convention.
Extend the mysql filter to enable filtering by locale
Conditionals should wrap around the entire filter block.
Localise the filtered announcements list

When viewing the localised version of announcements it's only possible
to filter on world location.  This is because rummager doesn't
support filtering on language so we have to use the older mysql
document filter.
Add translations for localised announcement filters
Add localised filtering of policies
Finally add localised version of the publications filters
Localised publication and policies lists should be minimal.

Rather than support full localised policies and publications filters
we're deliberately only enabling the minimal filtering required to
support 'view all' links from world locations.  This is for a few
of reasons:

First, the story I'm working on is only about the world location page;
localising the filters is the implementation, not the story.

Second, localised filters use the Mysql filterer, not rummager.  By
only providing minimal filtering, we potentially reduce the work
required to move over to rummager (as only the minimal filtering
we're using will need to be supported).

Finally, some features such as the results description have
deliberately been left off the localised versions.  This is because
descriptions like 'No results about Employment by Office of the
Advocate General from Angola relevant to local government
published 1 April 2013' are extremely difficult to translate into
other languages without writing custom code for each.
Merge pull request #293 from alphagov/localised-filter-lists

View all editions of a type for a particular language and world location

https://www.pivotaltracker.com/story/show/44634725