added convertions : std::pair<std::string,mapnik::value>  to Python tuple mapnik::value -> PyObject   
added convertions :
std::pair<std::string,mapnik::value>  to Python tuple
mapnik::value -> PyObject
  


git-svn-id: 5adfda8227e14e59fd47d5bd9925a30df16fed74@484 d397654b-2ff0-0310-9e29-ba003691a0f9

craigds/mapnik2,makinacorpus/mapnik2,makinacorpus/mapnik2,craigds/mapnik2,makinacorpus/mapnik2,craigds/mapnik2,makinacorpus/mapnik2,craigds/mapnik2