BUG: msct_register/register2d_columnwise: major refactoring and bug fixing
BUG: msct_register/register2d_columnwise: major refactoring and bug fixing

Former-commit-id: b275e9b8b0a1450c04f49ac484fa0239afd36b08 [formerly c1fb443a8730f176af6b7018299372d71fdf1363]
Former-commit-id: fbebb6b78fdf33220b022a74581ad72db22796c8
Former-commit-id: bbae846e763faa15efa5b91e6f7f91a06b7cec18
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox