DEV: improved u-net machine learning. Can now be trained. Still need experimentations
DEV: improved u-net machine learning. Can now be trained. Still need experimentations

Former-commit-id: 379874a97148ab79811397c1a68948a267dce279
Former-commit-id: 2e546ecca781edf23e1d2517d089e70a42f1df7b
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox