NEW: crop_by_slice feature to treat AMU data
NEW: crop_by_slice feature to treat AMU data

Former-commit-id: 14db238f86ad88c780cb0164badfece3c4fa4a27
Former-commit-id: b5f0a12a71245d353f0726688f19bae2d67bdd34
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox