OPT: co-register model data using images and not WM seg
OPT: co-register model data using images and not WM seg

Former-commit-id: e1455e6ea22345585743f0ec4111884b071a9b34 [formerly bc6a9db2db487f385badf3cfc3701eabb2c217d5]
Former-commit-id: 243f10722608679c77c75d2fc322ac94321347d2
Former-commit-id: b19773f5068faa6b3e9cc62c381a45ad2cffd608
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox