all time-based panels are now derived from a common base class

Cuts down on a lot of duplicate code between
TimelineWidget/ViewerWidget/CurveWidget/NodeParamView
and TimelinePanel/ViewerPanel/CurvePanel/ParamPanel since they all use similar
time functions.

app/widget/timelinewidget/view/timelineviewrect.cpp

@@ -46,9 +46,9 @@ void TimelineViewRect::SetTrack(const TrackReference &track)
   track_ = track;
 }
 
-void TimelineViewRect::SetScale(const double &scale)
+void TimelineViewRect::ScaleChangedEvent(const double &scale)
 {
-  scale_ = scale;
+  TimelineScaledObject::ScaleChangedEvent(scale);
 
   UpdateRect();
 }