Provide solutions for registration of lumbar data

[joshuacwnewton]

NB: This issue has been migrated from the spinalcordtoolbox repository: https://github.com/spinalcordtoolbox/spinalcordtoolbox/issues/3599

We should provide a satisfactory solution for every users working with thoraco/lumbar data. Currently, registration to the template is not easy.

Some thoughts:

• Create a cauda equinea label in the PAM50 template

Ref:

• https://forum.spinalcordmri.org/t/labels-for-lumbar-spinal-level/737/5