Adding mail attributes support.
Committed 7/5/2003 by Vincenzo, included in 2.2.0a9.
Adding some matchers/mailets that manage mail attributes from config.xml. Committed by Vincenzo 7/15/2003.
Implementing "forward" compatibility for mail attributes. Committed 7/17/2003 by Vincenzo.
DB repositories become "mail attributes enabled" by default. Committed 8/18/2003 by Vincenzo, included in 2.2.0a10.
Now during initialization will check if everything is OK in the database definitions for JDBC repositories support of mail attributes and behave accordingly. Committed 9/8/2003 by Vincenzo, included in 2.2.0a11.