REF: updated batch_processing -- need to fix issue related to concatenation of warping fields.
REF: updated batch_processing -- need to fix issue related to concatenation of warping fields.

Former-commit-id: e1fbd7734795ebbcfc333e3deed3663d9f72339c
Former-commit-id: 70da99b76a619f269d7af6fcdc193efc9f2db768
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox