JetPack 4.6.3

Update README.md

Update jetson_variables copyright date

Update README with Jetson models

Cleanup readme

Merge pull request #5 from jetsonhacks/L4T32.3.1

Update to JetPack 4.3

Support for JetPack 4.1.1

Update README

Update README for Xavier

L4T 28.2.1 cleanup