Revision 1336

 Fixes RTbug #1973, 1971.
(Classification.SetField, Classification.SetFieldType):
        Replaced with SetFieldInfo.
(Classification.SetFieldInfo): New. Does a better job of
        what SetField and SetFieldType used to do by combining
        their function since they should really always be done
        at the same time.
(Classification.SetLayer): Renamed to _set_layer.
(Classification._set_layer): Should only be called from
        Layer's SetClassification. This does not cause a recursive
        call as SetLayer did because we know that Layer knows about
        the classification.