backend : add save on clsing

BellwetherBackend/MainWindow.xaml.cs

@@ -26,6 +26,13 @@ namespace BellwetherBackend
         public MainWindow()
         {
             InitializeComponent();
+
+            Closing += MainWindow_Closing;
+        }
+
+        private void MainWindow_Closing(object sender, System.ComponentModel.CancelEventArgs e)
+        {
+            SaveCurrentPage();
         }
 
         private void RadioButton_Checked(object sender, RoutedEventArgs e)