feature request - skip login screen if login credentials supplied elsewhere

[liamr]

In our environment, our login credentials are supplied by our Web ISO / 
SSO, CoSign (weblogin.org).  It would be very cool if roundcube would 
recognize when such things are set (say... $_SERVER['REMOTE_USER'], or 
$_SERVER['PHP_AUTH_USER'] & $_SERVER['PHP_AUTH_PW']) and skip the login 
screen, logging into the IMAP server w/ the provided credentials.

Liam