[io] take into account all the shapes defined in a step file for computing properties (mass, com, inertia)
[io] take into account all the shapes defined in a step file for computing properties (mass, com, inertia)

radarsat1/siconos,fperignon/siconos,siconos/siconos,siconos/siconos,radarsat1/siconos,fperignon/siconos,fperignon/siconos,fperignon/siconos,radarsat1/siconos,siconos/siconos,radarsat1/siconos,radarsat1/siconos,siconos/siconos,fperignon/siconos