Autologin: Remove deprecated autologin methods

Remove methods from manager because autologin
is now handled with special backends (AutoLoginBackend).

The session is used to store the status about a remote
user authentication to send a 401 header to the client
upon logout.

refs #6461
Autologin: Fix javascript logout code

Window onload event handler comes to late. Change
part of the code to use jQuery.

refs #6461
Merge branch 'bugfix/autologin-logout-6461'

fixes #6461