Stop organisations in meta footer clashing IDs

Because we use `content_tag_for`, the IDs are automatically generated. We can work around this using the [prefix argument](http://api.rubyonrails.org/classes/ActionView/Helpers/RecordTagHelper.html#method-i-content_tag_for), but that should only be overridden in the template, since the helpers won't know how to do this correctly.

The problem this causes is that there are two things with IDs of `organisation_1234` on the publications page, as the organisation is shown more than once.