Update Map-API docs
Update Map-API docs

It was not clear to me what the difference was between a mapnik layer and a cartodb layer until I read the comments in the Mapconfig spec! Let's save some users the extra step :)
UCL-ShippingGroup/Windshaft-cartodb,CartoDB/Windshaft-cartodb,manueltimita/Windshaft-cartodb,manueltimita/Windshaft-cartodb,UCL-ShippingGroup/Windshaft-cartodb,manueltimita/Windshaft-cartodb,CartoDB/Windshaft-cartodb,CartoDB/Windshaft-cartodb,UCL-ShippingGroup/Windshaft-cartodb,CartoDB/Windshaft-cartodb