File README.SUSE of Package nullmailer

This package deviates from the original installation method in a few respects:
- configuration lives in /etc/nullmailer
- the spool directory was moved to /var/spool/nullmailer
- the service directory was moved to /usr/lib/nullmailer
- the daemon is run as user/group mail/mail not nullmail/nullmail
- a SYSV init script was added, that's the preferred method for managing services on openSUSE