Add missing files from panda-dist.tar.gz

[bictorv]

There are files missing from panda-dist.tar.gz at http://panda.trailing-edge.com/, which I think would be good to add to this repo for completeness. Examples are CPYRIGHT, README, README-MULTIUNIT-RP07; perhaps also RH20.RP07.1. (No need to include the klh10-2.0h and executables based on that, of course.)