keyframeview: implemented transforming keyframe times to and from sequence time

Since the node graph can have transform cross nodes, input keyframes may occur
at a different times requiring transforming between sequence time and media
time. This commit implements such a mechanism in all UI classes that need it.

app/panel/param/param.cpp

@@ -28,6 +28,7 @@ ParamPanel::ParamPanel(QWidget* parent) :
 
   NodeParamView* view = new NodeParamView();
   connect(view, &NodeParamView::SelectedInputChanged, this, &ParamPanel::SelectedInputChanged);
+  connect(view, &NodeParamView::TimeTargetChanged, this, &ParamPanel::TimeTargetChanged);
   SetTimeBasedWidget(view);
 
   Retranslate();

app/panel/param/param.h

@@ -36,6 +36,8 @@ public slots:
 signals:
   void SelectedInputChanged(NodeInput* input);
 
+  void TimeTargetChanged(Node* node);
+
 protected:
   virtual void Retranslate() override;