REF: use label/ as default for path to template (and check folder existence)
REF: use label/ as default for path to template (and check folder existence)

Former-commit-id: f71d088fb820a59cd54cfe63ea84d36b8d54b607 [formerly cfb30576226086d1eeb7da9a33280c2f747dc3b6]
Former-commit-id: 0159830a03ee7551af8776514b717bda02a83352
Former-commit-id: a453ae9dd3d505f290b2e6320a705634a619a029
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox