Add QueryWindow

Elwig/Windows/MainWindow.xaml.cs

@@ -47,5 +47,10 @@ namespace Elwig.Windows {
             var w = new TestWindow();
             w.Show();
         }
+
+        private void QueryWindowButton_Click(object sender, RoutedEventArgs evt) {
+            var w = new QueryWindow();
+            w.Show();
+        }
     }
 }