OPT: maths: added dilation/erosion
OPT: maths: added dilation/erosion

Former-commit-id: eb64b8c2d855f54a03ff6763578da2a7faa61a19 [formerly 5a0aa03838a5da871d88ae5c95b03b8fb73fe17d]
Former-commit-id: 61388915b2532bc58fe9f0254226fda3eb4c6b32
Former-commit-id: 36a5c435c4dfa59c45d51fd9331b954035d4dc37
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox