add helper to generate stats on QCM questions distribution
add helper to generate stats on QCM questions distribution

sativouf/qcmffvl,jruffet/qcmffvl,sativouf/qcmffvl,jruffet/qcmffvl,satiruf/qcmffvl,jruffet/qcmffvl,jruffet/qcmffvl,satiruf/qcmffvl,satiruf/qcmffvl,sativouf/qcmffvl,sativouf/qcmffvl,sativouf/qcmffvl,satiruf/qcmffvl,satiruf/qcmffvl,jruffet/qcmffvl