add Poly::Visitor to visit multiple types with same polyvisit function
add Poly::Visitor to visit multiple types with same polyvisit function

fperignon/siconos,fperignon/siconos,radarsat1/siconos,radarsat1/siconos,bremond/siconos,siconos/siconos-deb,fperignon/siconos,bremond/siconos,bremond/siconos,siconos/siconos-deb,siconos/siconos,radarsat1/siconos,radarsat1/siconos,siconos/siconos,bremond/siconos,siconos/siconos,siconos/siconos,fperignon/siconos,bremond/siconos,radarsat1/siconos,siconos/siconos-deb,siconos/siconos-deb,siconos/siconos-deb,fperignon/siconos,siconos/siconos-deb