validation on local news for location and world offices

https://www.pivotaltracker.com/story/show/45878105
Rename WorldwideOfficeType sort_order

To be inline with the exisiting orgs listing_order
Merge pull request #353 from alphagov/validation-on-world-locaiton-news

Validation on world location news so that location and organisation are present

https://www.pivotaltracker.com/story/show/45878105