* Update repo to use LUFA as a git submodule
  * `/lib/LUFA` removed from the repo
  * LUFA set as a submodule, pointing to qmk/lufa
  * This should allow more flexibility with LUFA, and allow us to keep the sub-module up to date, a lot more easily.  It was ~2 years out of date with no easy path to fix that.  This prevents that from being an issue in the future