Function geo_layer_from_aux_substations 

pub fn geo_layer_from_aux_substations(aux: &AuxFile) -> GeoLayer

Lift the aux Substation table into a geographic GeoLayer with substation targets keyed by substation number. The number comes from SubNum or Number and the point from Latitude and Longitude, the column names PowerWorld writes itself, so they take no aliases. A row whose number or coordinate is absent or is not a finite number is skipped. Rows stay in file order, so a repeated substation number keeps the last point once apply_substation_points runs.