refs #3813 css files in libs folder should always be included first, …

…so they can be overwritten in piwik css as clean as possible

core/AssetManager.php

@@ -188,9 +188,9 @@ private static function getCssFiles()
     private static function sortCssFiles($cssFiles)
     {
         $priorityCssOrdered = array(
+            'libs/',
             'themes/default/common.css',
             'themes/default/',
-            'libs/',
             'plugins/',
         );