Corporate Info translation tests more generic

A stepping stone to allow us to use both worldwide organisations and
regular organisations in this controller.

Removed one check for a link that is better tested via the cucumber
feature.
Remove more references to WorldwideOrganisation
Start using controller for org CI translations
Corp info pages now translatable for orgs

Reused the existing `corporate_information_pages_translations`
controller code to do this, turning many of the urls into polymorphic
associations. Reworked the tests into a set of helpers which can then be
called for both worldwide_organisations and regular organisations.
Remove redundant whitespace

Thanks @bradleywright
Merge pull request #370 from alphagov/corp-info-pages-translatable-for-orgs

Corp info pages translatable for orgs

https://www.pivotaltracker.com/story/show/44081009