TEST: added accuracy computation in testing of straightening
TEST: added accuracy computation in testing of straightening

Former-commit-id: 60027f8a6fb50e8d052fef601112eae50748239b
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox