inbox and outbox for direct messages

Added an inbox and outbox for direct messages.

Factored common code to mailbox.php. Factored common code with
stream.php to personal.php.

darcs-hash:20080916195346-84dde-b5c846f713a970c41fd1b0671cb333e91f3cb920.gz

lib/util.php

@@ -869,6 +869,8 @@ function common_fancy_url($action, $args=NULL) {
 	 case 'subscribers':
 	 case 'all':
 	 case 'replies':
+	 case 'inbox':
+	 case 'outbox':
 		if ($args && isset($args['page'])) {
 			return common_path($args['nickname'].'/'.$action.'?page=' . $args['page']);
 		} else {