jQuery is not available here because JavaScript is loaded after the content.
This was no problem before because the logout action was submitted using XHR and thus having JavaScript.
refs #8626
Provide a new settings authenticationMode and delegate the
authentication handling to the webserver when the external authentication mode
is set. Add a new view 'logout' that will be shown after logout from external
authentication as the regular redirect to login is not possible.
refs #5405