Rdmo

* enable collaborative editing
* refactor tests

- add shibboleth settings
- add shibboleth documentation
- add promote-user-to-superuser command

- fix bug with subsection title
- fix typos

- fix migrations

- refactor models to use URI, URI Prefix, and Key
- refactor tests, remove factory_boy
- add test fixtures
- add XML export
- add XML import
- fix i18n switcher
- fix dates in project_answers_tree
- fix yes/no widget

After running the migrations, use


./manage.py set-uri-prefix 'https://example.com/terms'


(with example.com replaced by your domain) to initialize the URI.

- fix i18n switcher
- refactor project_answers