Added the configuration variable $conf['demo_mode'] in the config.inc.php file. It disables the newly introduced demo mode which limits certain actions in the interface part of ispconfig: the demo mode can be used to run the ispconfig interface part as online demo.

Fixed: when creating a cp user with modules "mail,dns,sites" and start module "monitor" he gets "LOGIN_REDIRECT:/index.php" after login in.
Added: Better username regular expression check.

- Changed shell of website linux user to /bin/false