Order worldwide organisations by name in admin
Nicer admin index page for worldwide organisations
Move worldwide organisation translations to a tab
Add enclosing object id tag for worldwide orgs
Add translations column to worldwide org index
General purpose helper for flagging deprecated columns
New model for featuring

A feature list is a collection of featured items. This commit
contains the models for featuring things on world locations.

It has a polymorphic association to a featurable so it can be used for
featuring on any object.

Rather than building featuring mechanisms separately for every object
type which can have featured things, I'm making a general purpose
featuring mechanism.

Hopefully we'll able to refactor the other featuring things to use
this featuring mechanism in the future.
Remove old method of featuring on world locations

The featuring abilities on edition_world_location are no longer needed
as they are being replaced by the new feature_list mechanism. We can
also delete edition_world_location_image_data completely, it's not
needed.

The new featuring mechanism features documents rather than editions, so
there's no need to separate the attachments from the feature model (so
we don't need feature_image_data).
User interface for world location featuring

Add the user interface to manage features independently for each locale of a
world location.

I've introduced a new tabbed view of world locations and improved the
world location index page admin.

The controllers and views for feature lists and features stand alone
from world locations so they could easily be used for managing
featurings on other object types in the future.

The frontend code introduces a feature list presenter to present
features correctly.
Acceptance tests for independent featuring

Test explicitly that we can feature independently on each locale, and
that the correct translation is displayed.

I added an extra css 'feature' class to featured items to facilitate
testing.