Investigate use of Shapely for exporting Points coordinates

[will-moore]

From #173 (comment)
In the Batch_ROI_Export script, we could look at the option to export a simplified Polygon, to preserve the shape but without a long list of coordinates. See https://shapely.readthedocs.io/en/latest/manual.html#object.simplify
As used at by Vitessce, see https://docs.google.com/presentation/d/1QzKYP6sXPefBMNfY4PW4H0AMoWVbw9HeNoweLmJg17Y/edit#slide=id.g823da5adf3_0_105