Redesign admin edition show page

https://www.pivotaltracker.com/story/show/53973095

The main change is that you can no longer preview documents and document metadata on the admin edition page – you have to go to the preview on the frontend.

This includes the start of some cleanup of the admin CSS. The huge global CSS files can be migrated to helpers or views, similar to frontend CSS.

Worldwide organisations have been added to the document metadata on the frontend. This is mainly to fix the tests because they're no longer in the admin, but according to Neil they should be there anyway.

Known issues which should be separate stories:

- Supporting pages need a cleanup, similar to how translations have been done
- Some buttons have a `data-confirm` attribute on them to show a confirm message, but this does not seem to work.