cache images in global tmp directory

app/modules/cachedimage.php

@@ -5,7 +5,7 @@ namespace Modules;
 class CachedImage {
 
     public $original;
-    public $cache_dir = "rsc/img_display/";
+    public $cache_dir = "tmp/";
     public $default_width = 500;
 
     function __construct($path) {