Implemented: FS#973 - Gentoo support for installer. Fixed FS#974 - Directory mode for firewall configuration

- fixed a php notice in app.inc.php

Disable spam and virus notifications for the admin user. Can be overridden by the policies in mysql.

2.) Cleaned up update.php
3.) Changed definitions for quarantine settings
4.) Commented out areas for quarantining 'clean' and 'other'