POC GPU Docker -> Singularity For Medical Group

[bitfort]

Demo Includes:

1. Starting with the CUDA BRATS Docker Template (https://github.com/BraTS/Instructions/tree/master/docker_templates/template_2020) 1a. MLCube the example
2. Build this docker image and materialize it on disk
3. "Convert" to a singularity image (this may be a technical "no-op" but a semantic concept only)
4. Run using singularity & no sudo on GPU
5. Follow up: show the same works for podman.