Revert "REF: Make 'step' mandatory. See issue #1034"
Revert "REF: Make 'step' mandatory. See issue #1034"

This reverts commit c4e7077f02cf6490cdfc9bfb33d495c7e2c9e6e0 [formerly 13a94f59beed64e19f2c663f0bc0db16e0e43d6e] [formerly baca0e82ddfc185987ec9eee1db890eecb68077b] [formerly 59885d694c726e0a5a3fb7c71a3132d9da90d3f0 [formerly e2de43324daf8c216da82bc3df70c7cf4e592066]].


Former-commit-id: 6671a681601d69058931b107fd990360d398b49d [formerly bc5ed5e60b06555c075e24cc5ad19674d24babdd]
Former-commit-id: c2bbb159f68f1f1459112928bf26a8ebad860371
Former-commit-id: 2a2a0ccf49b15e73cd8501d0bcde5fef373a4c7d
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox