use client?s mimetype as fallback for uploads

www/analytics/plugins/ExamplePlugin/javascripts/plugin.js

@@ -0,0 +1,20 @@
+/*!
+ * Piwik - Web Analytics
+ *
+ * @link http://piwik.org
+ * @license http://www.gnu.org/licenses/gpl-3.0.html GPL v3 or later
+ */
+
+$(document).ready(function () {
+    /**
+     * Please note that this JavaScript file will be loaded only if you
+     * enable the following setting in your config:
+     *
+     * [Debug]
+     * disable_merged_assets = 1
+     */
+
+    if('undefined' != (typeof console)) { /* IE8 has no console */
+        console.log('Plugin file loaded');
+    }
+});