Fixed registration issue caused by labels far from cord centerline (#1828)
Fixed registration issue caused by labels far from cord centerline (#1828)

* started implementing fix for 1826 (unfinished)

* now projects labels onto centerline to account for disc labels (fixes issue 1826)


Former-commit-id: 08ac7713b55a8efe8405527695ea4a2736ad908c
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox