NEW: registration pipeline for group study
NEW: registration pipeline for group study

Former-commit-id: d0a00b47030af548b3e352281b360f825bc171b2
Former-commit-id: 5c5de4c761f1bf3f483385c5d4d54ae283232ddb
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox