First pass at translating corporate information pages for worldwide.

Corporate information pages can also be associated with normal (i.e.
non-worldwide) organisations, but here I've only added behaviour for
translating those which are part of the worldwide site.
Translate labels for corporate information pages on worldwide.

Note the use of `_html` keys in the translation keys - this lets us
interpolate HTML (e.g. links) without having them escaped.
Merge pull request #296 from alphagov/translate-worldwide-office-corporate-information-pages

Translate worldwide office corporate information pages

This is work towards: https://www.pivotaltracker.com/story/show/44872957