Since there is no demo or us site anymore we can simplify the structure
somewhat by moving the sandbox one directory up

- Use i18n URLs
- Add breadcrumbs

I used the existing script [1] that cooperates very nicely with vim.
1: https://github.com/rory/django-template-i18n-lint

Fixes #676

Example sites now sit in their own folder (sites) for easier
organisation.

This allows members of the public to play around with the dashboard
site.