OPT: if last transformation is an affine transfo, cropping is not done (because we don't know how) but user is warned
OPT: if last transformation is an affine transfo, cropping is not done (because we don't know how) but user is warned

Former-commit-id: 1aacb5b4d4e013aeb4e6c5c3c7f7b8d7f62a9a80 [formerly c86f6616e05b429fc9d809e9c04da1bf498b755e]
Former-commit-id: 75672ea5220b3e05e33b05e6942e6784e9a2e16f
Former-commit-id: 22d7904dadd34ab9ea38519d3a588681754a5b1e
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox