OPT: improve organization of the output Excel file
OPT: improve organization of the output Excel file

Former-commit-id: af3f3cd40807a60e89f901e2b2a5c88857297dbb [formerly 68536e21eb76f790fc9fbeded299989464d28425]
Former-commit-id: d66ff58fe470dbc6afa8eaf081df9cb48d955bed
Former-commit-id: 53b1e5ead60008db1bda789dd3422043a74906e2
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox