[io] introduce normalcone-ratio options for separate scaling w.r.t contact forces      add small documentation
[io] introduce normalcone-ratio options for separate scaling w.r.t contact forces
     add small documentation

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