fill out default values in the 2.0.0 ref
fill out default values in the 2.0.0 ref

florianf/mapnik-reference,mapycz/mapnik-reference,florianf/mapnik-reference,mapnik/mapnik-reference,CartoDB/mapnik-reference,mapnik/mapnik-reference,mapycz/mapnik-reference,mojodna/mapnik-reference,mojodna/mapnik-reference,CartoDB/mapnik-reference,mapnik/mapnik-reference