[bp/r51261][FIX] Restore Mail Queue functionality that was lost when htmlMimeMail.php was retired some time ago. Save messages to the database and send them later by running sendmail.php from cron.

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/12.x@51262 b456876b-0849-0410-b77d-98878d47e9d5