OPT: now smoothing along centreline before registering to template
OPT: now smoothing along centreline before registering to template

Former-commit-id: 0598a793458d882cc6cae83dc5aeb5fb27fdab99
Former-commit-id: c0b3bd06f746324b31a0ee6637e12dcd99eddc80
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox