NEW:  add split and concat to sct_image
NEW:  add split and concat to sct_image

Former-commit-id: f9af1f0dd11afb72c8bc960c6e6681df00215f28 [formerly 56402d0b8bd1dec7d5f34c7f05283c7215f3d490]
Former-commit-id: 290d7750caf7b5064d4877dbc34e4d5f23fdffa3
Former-commit-id: b371b07f591b938d26629d7d6abcaca99cfeb222
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox