OPT: remove the use of the class param in function read_label_file in order to allow to use the function in other scripts -- FOR THE FUTURE, CLASS PARAM MUST ONLY BE CALLED IN FUNCTION "MAIN"
OPT: remove the use of the class param in function read_label_file in order to allow to use the function in other scripts -- FOR THE FUTURE, CLASS PARAM MUST ONLY BE CALLED IN FUNCTION "MAIN"

Former-commit-id: 7d9feb32abcd84d995952287e49f4db31426aace
Former-commit-id: 157c0a92994e0fafef95443e6eaedaf50687c2e8
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox