feedback on l4t-base container image

  1. DO NOT remove the older versions/tags when you release a new version
  2. provide versions with CUDA 8, CUDA 9, CUDA 10.0, CUDA 10.1
  3. provide images based on xenial AND bionic
  4. reduce the size (it has more than 1 Gb when expanded)

By the way, how do I install cuda on this image? It only has the stubs