Add ST_ToMultiLine

This seems to be possible in PostGIS only by doing something like

        SELECT ST_Multi(ST_Union(the_geom)) FROM myTable;
Add ST_Holes
Add ST_ToMultiSegments

This seems to be complicated in PostGIS. See
http://stackoverflow.com/questions/7595635/how-to-convert-polygon-data-into-line-segments-using-postgis