Show disk content separately inside the usage graph

src/js/index.js

@@ -272,6 +272,13 @@ app.filter('prettyMemory', function () {
     };
 });
 
+app.filter('prettyDiskSize', function () {
+    return function (value) {
+        if (value < 1024 * 1024) return (value/1024/1024).toFixed(2) + ' MB';
+        return (value/1024/1024/1024).toFixed(2) + ' GB';
+    };
+});
+
 app.filter('installationActive', function () {
     return function(app) {
         if (app.installationState === ISTATES.ERROR) return false;