Rename WorldwideOffice => WorldwideOrganisation

And all attendant associations etc.  Only models for now, controller & view code comes later.
Change views and controllers to use WorldwideOrganisation

Features and locales still use worldwide office.  We'll do them next.
Use worldwide_organisation as keys into translations
Update features to use renamed WorldOrganisation model/routes/ui
Inject a new WorldwideOffice between WorldwideOrganisation and Contact

The rationale is that we imminently need to add some more information to a contact when it's related to a worldwide organisation, but this information isn't relevant for any other contactable type, so we want a new object type.  WorldwideOffice is the best name because this thing does actually represent a single office.
We don't manage contacts for worldwide orgs, we manage offices

Transition the admin UI over from letting the user manipulate contacts to letting them manipulate offices instead.  Some of the code here is slightly awkward because there's nothing on a worldwide office that needs manipulating yet, and we have to keep referencing office.contact to show things.

There might be scope to introduce delegation of methods from worldwide_office instances down to their contact instances in a future commit, but the contact API is quite wide.
Update frontend to deal with offices, not contacts
Fix contacts controller test

Use organisations as the source model for contacts now that we don't add contacts directly to a worldwide org anymore.
Remove main contact stuff from admin contact partial

Only worldwide orgs had main / other contacts, and now that is applied to their offices not their contacts directly.  So we are able to remove the main contact button and heading notification from the shared contact partial as nothing uses it anymore.
Fix cucumber in light of office / contact changes
Add WorldwideService and WorldwideServiceType

Worldwide service is a service that a worldwide office offers, worldwide service type is a way of grouping these services by type.  We also have a data migration to seed the initial set of services (taken from comments on https://www.pivotaltracker.com/story/show/44233659).
Allow a worldwide office to have a list of services it provides
Provide UI for setting services on a worldwide office
Present services on the public facing views for an office

Using a ContactPresenter to make WorldwideOffice instances look enough like a Contact that we can continue to use the contacts/_contact partial.  This presenter delegates everything to the contact if it's there, otherwise it delegates to the model as usual.

Have added the display of services to this partial (it's robust enough to work for Contact instances or Contact instances wrapped in a ContactPresenter.

This most definitely needs some styling.
Fix syntax error in migration
Add missing index to schema.rb
Remove redundant code
Extract method
Simplify contact_number param cleaning
DRY up contact form fields