* Add render_views for admin/settings spec

* Add coverage for admin/settings#update

* Add coverage for admin/settings typecasting open_registrations setting

* Simplify how admin/settings finds the value for updating

* Rely on activerecord to not update a value that hasnt changed

* Add coverage for non-existent setting

* Use a constant for boolean settings

* Add Admin::BaseController to wrap admin area

Extracts the setting of the `admin` layout and verifying that users are admins
to a common base class for the admin/ controllers.

* Add basic coverage for admin/reports and admin/settings controllers