OPT: created new function in sct_utils to generate appropriate field for interpolation method depending on program used. Also updated sct_apply_transfo.py in order to accept interpolation option
OPT: created new function in sct_utils to generate appropriate field for interpolation method depending on program used. Also updated sct_apply_transfo.py in order to accept interpolation option

Former-commit-id: c1fd12b0c2d6df815a002cedf93674767a85688e [formerly 7cb13cbedab62af2d81af40358f8886e6cfec1ea]
Former-commit-id: 259bf0df1aaebd754e6690cd63e2ee4e8a701e04
Former-commit-id: b81af55fffe76ce55d045eba15457a8158c38e9a
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox