OPT: output landmarks as .nii.gz for faster execution (HD access) + now write landmarks as int32 (previously uint8)
OPT: output landmarks as .nii.gz for faster execution (HD access) + now write landmarks as int32 (previously uint8)

Former-commit-id: 260ba782cf2601717ece88a93f01df58fb3117c5
Former-commit-id: a02334b3d038e6377b0186205b36dda0362a4384
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox