Resolve WB-488: Scenes preserve the charts rather than the method to...

Resolve WB-488: Scenes preserve the charts rather than the method to regenerate the files: The scenes still save and load the actual chart points.  However, when the scene is restored, it will attempt to reload the chart data from the data file and, if successful, the points from the file will be used for the chart.  In the event the points cannot be read from the file, the chart points that were saved to the scene will be used and the user will receive an error message.