Add stats output to input shapefile

[andreas-h]

When computing statistics, it would be great if optionally, the results would be written directly to the input shapefile instead of creating an extra csv file. Something like

starspan  --vector input.shp --raster ~/data/popdens_sedac.tif --stats avg:"mean" std:"std" --out-type add_to_vector

which would calculate average and std, and add the results to the input.shp file in columns mean and std.