Large restructure of SASL authorization and some SASL authentication changes:

 * Implemented PLAIN SASL Server 
 * Moved PLAIN auth to using SASL Server object
 * Allow case for client EXTERNAL auth
 * Created AuthorizationMappings (allow for default usernames different from 
      principal used)
 * More robust handling of LDAP authorization (allows JID != principal)
 * Fixes case sensitivy issue with default authorization policy
 * Removed UnixK5LoginPorivder, since it will likely never be used, has never
      been tested, and would be difficult to maintain in the long run.

The Loose, Lazy, and Strict policies have been removed, and folded into a 
single Default policy that now resides in 
org.jivesoftware.openfire.auth.DefaultAuthorizationPolicy

Issues: JM-1079 JM-1086



git-svn-id: http://svn.igniterealtime.org/svn/repos/openfire/trunk@8583 b35dd754-fafc-0310-a699-88a17e54d16e