Allow plugins to set class attribute for preferences section

program/steps/settings/func.inc

@@ -157,7 +157,7 @@ function rcmail_user_prefs($current = null)
     $no_override = array_flip((array)$RCMAIL->config->get('dont_override'));
 
     foreach ($sections as $idx => $sect) {
-        $sections[$idx]['class'] = $idx;
+        $sections[$idx]['class'] = $sect['class'] ?: $idx;
 
         if ($current && $sect['id'] != $current) {
             continue;