This adds the extensibility to customize the prepended signature in the Subject via the config. It also includes the ability to include the score in the signature as well as include a space in the signature. The issue of the space comes as the config parsing requires "mod 2" and I was lazy.
I propose in the TODO the ability to clock the time it takes for spamd to scan an email. A month or so ago there was a thread about this and I forgot I had such a mechanism in my spamassassin plugin. Rather than pollute this patch with its already suspect sprintf and sed. I can submit that as a subsequent patch. http://peter.boku.net/qpsmtpd/spamassassin.diff
