optimizations (php only)

- removed unnecessary call to array_unique in get_image_ids_for_tags
- put back in smarty exec time counting (debug mode) for each included template
- prefix some smarty modifiers with @ in some templates
- do not call format_date (still very slow due to mktime and date even after prev commit) from category_default.inc.php - if used in templates format_date can be used as a smarty modifier

git-svn-id: http://piwigo.org/svn/trunk@3120 68402e56-0260-453c-a942-63ccdbb3a9ee

include/functions_tag.inc.php

@@ -189,8 +189,7 @@ SELECT image_id
       {
         $items = array_intersect($items, $images);
       }
-
-      return array_unique($items);
+      return $items;
       break;
     }
     case 'OR':