implemented vertical "zooming" in the TimelineWidget and CurveView

This comes in the form of changing the vertical scale in the CurveView and
adjusting all track heights in the Timeline.

app/widget/curvewidget/curvewidget.h

@@ -28,6 +28,9 @@ public:
   const double& GetScale();
   void SetScale(const double& scale);
 
+  const double& GetVerticalScale();
+  void SetVerticalScale(const double& vscale);
+
 signals:
   void TimeChanged(const int64_t& timestamp);