OPT: label_utils: now possible to add all labels for vertebral levels
OPT: label_utils: now possible to add all labels for vertebral levels

Former-commit-id: 2a559ac2dc18b2ba5e776ea7c8eae9b47481f1fb
Former-commit-id: bd67535b50f62c02a34bdf01959f50bea9039c16
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox