Item12823: mark cron-generated mails as per RFC 3834 and (more importantly) fix the unit test suite so it actually detects and reports the wrong mails being sent out

git-svn-id: http://svn.foswiki.org/branches/Release01x01/MailerContrib@17449 0b4bb1d4-4e5a-0410-9cc4-b2b747904278