Support mouse gestures when active tracing is enabled (#1064)

* Make the pointer follow the mouse

* Only render when necessary

* Move trace rendering to background thread

src/GraphControl/Control/Grapher.h

@@ -333,6 +333,7 @@ public
         bool m_KeysPressed[5];
         bool m_Moving;
         Windows::UI::Xaml::DispatcherTimer ^ m_TracingTrackingTimer;
+        Windows::UI::Core::CoreCursor ^ m_cachedCursor;
 
     public:
         Windows::Storage::Streams::RandomAccessStreamReference ^ GetGraphBitmapStream();