Editable world location titles in English.

We'll need to be able to change these in English, as well as in
any translations. I didn't spot that I hadn't added the field to
the normal form as well as the translation.

https://www.pivotaltracker.com/story/show/44462901
Merge pull request #217 from alphagov/edit-world-location-titles-in-english

Editable world location titles in English.

This completes: https://www.pivotaltracker.com/story/show/44305883