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

Former-commit-id: 51de506b21a43e9b4731b2e090d2c8191b721cc6 [formerly de3689cc906c6d59948cfcca09911c32ecb2762e]
Former-commit-id: 3d86cc75ff8f3052b92de04c60271d5a40d14154
Former-commit-id: f89f4847865789ccc847a62f69cfdd1426f36496
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox