Render links to locations and worldwide orgs on document show page

Use feature switching to make sure this only happens once world is live.
Rename world_location_news_feature? to world_feature?

We'll be using it to control revealing all the world stuff so it makes sense that it's a more generic name.
Fix PDFInfo test that was failing on travis

Don't know why it was failing as I've not touched it, but this should make it work.
Merge pull request #368 from alphagov/world-loc-and-office-links-on-doc-pages

World loc and office links on doc pages

https://www.pivotaltracker.com/story/show/42850055