REF: msct_register: moved register_seg from msct_register_regularized
REF: msct_register: moved register_seg from msct_register_regularized

3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox