Add chart data export to Plotly Studio

[David Platten]

Some users may wish to edit or customise the built-in charts. This can be done by exporting the chart to Plotly Studio (https://plot.ly/create) and then editing it there.

A link can be included below each chart, sending the data to Plotly Studio, by adding the following line to the plot() command:

show_link=True,

As this involves exporting the chart data to an on-line resource outside the control of the OpenREM server I propose this is controlled using an OpenREM administrator chart option, where the export links can be turned on or off.