Remove STDEV, STDEVP from SHARED_DOMAIN_OPS + add comments
Remove STDEV, STDEVP from SHARED_DOMAIN_OPS + add comments

uwdata/vega-lite,uwdata/vega-lite,uwdata/vega-lite,vega/vega-lite,vega/vega-lite,uwdata/vega-lite,vega/vega-lite,vega/vega-lite,uwdata/vega-lite,vega/vega-lite