[examples] n_cubes.py appears to need more multipoints iterations
[examples] n_cubes.py appears to need more multipoints iterations

Even with increased multipoints iterations, sometimes cubes fall
through the floor.  Sliding appears to be problematic for Bullet's
convex-convex algorithm.  But it seems more robust with these values.

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