associate users to world locations
filter editions by world locations in the admin interface

need to clean up specs
clear world locations on a admin user
Admin frontend for filtering docs by world location
Fix publishing search test

so it doesn't fail when running all unit tests
Merge pull request #291 from alphagov/worldwide-editors-admin

Filter admin list of documents by a writer's world location

https://www.pivotaltracker.com/story/show/45150733