NEW: oo segment_graymatter beta added
NEW: oo segment_graymatter beta added

Former-commit-id: a503b2b6bba615a0189968a4b9f89f4c3816f77d
Former-commit-id: 9888d9cc3289a78e60cda111ade60d1415568a4c
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox