added context menu to download folders

mainwindow.h

@@ -121,7 +121,7 @@ class MainWindow : public QMainWindow
 
         void on_listWidget_clicked();
 
-        void on_treeWidget_itemClicked(QTreeWidgetItem *item);
+        void on_treeWidget_itemClicked(QTreeWidgetItem *item, bool downloadDir = false);
 
         void downloadFinished();
 
@@ -141,6 +141,8 @@ class MainWindow : public QMainWindow
 
         void on_action_Settings_triggered();
 
+        void on_actionDownload_triggered();
+
 public slots:
         void on_buttonBox_accepted();