Usage:
  weighted_average_raws.php?area=name&ids=id_list&cats=cat_list&weights=weight_list&day=day_to_get&month_to_get&year=year_to_get=
    where:   
                area = name asigned to group of RAWS stations
             id_list = a comma-separated list of RAWS stations by WIMS id 
            cat_list = a comma-separated list of WIMS climate/fuel identifiers corresponding to the id_list stations
         weight_list = a comma-separated list of weights to apply to the stations in the id_list 

    the following are optional parameters can be omited if you only want the latest data:
          day_to_get = day to retreive
        month_to_get = month to retreive
         year_to_get = year to retreive