OPT: sct_extract_metric: added mlwath
OPT: sct_extract_metric: added mlwath

Former-commit-id: cb5821c4dcde2aff418045e4f08e351106a61deb [formerly 6feb7165b491c73e9db469789edbe4fa3eed4d01]
Former-commit-id: 8700da155510721501085a3caeda2bef2f550861
Former-commit-id: 3c201b7989735b84c28d3fc34162ee16661911e6
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox