http://jira.springframework.org/browse/SEC-1023.
hasPermission() now delegates to a PermissionEvaluator interface, with a default implementation provided by the Acl module. The contacts sample now uses expressions on the ContactManager interface. The permission-evaluator element on global-method-security can be used to set the instance to an AclPermissionEvaluator. If not set, all hasPermission() expressions will evaluate to 'false'.
