OPT: sct_register_to_template: added param for zsubsampling
OPT: sct_register_to_template: added param for zsubsampling

Former-commit-id: f7cc6a7ab7e2cf3eb56dd2605699a895cbbdd56e [formerly 78ed516ffca6d2c28aec25c65411bc5311e8c9dd]
Former-commit-id: 869997e57680619893817c092e80b4b90c4589a7
Former-commit-id: 53996a410a707dced8f35ff39d69f3e4cb4096d7
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox