OPT: sct_extract_metric: added robust ML estimation followed by WA after correcting for PVA (mlwa)
OPT: sct_extract_metric: added robust ML estimation followed by WA after correcting for PVA (mlwa)

3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox