[mechanics] remove import of occ class at module level
[mechanics] remove import of occ class at module level

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