testing betterproto + grpclib for more pythonic code and asyncio

[quite]

I've tried out betterproto as an alternative to the protoc python (branch betterproto-test). Together with grpclib's asyncio based calling, it looks quite nice and much more pythonic, snake_case, etc. Some differences are that the calls typically take only keyword args, and all our proto-files are baked into one python package "base" (we do have package base; in every file!).

I've ported the simple ecu.py along with only the helpers that it used. See the diff: master...betterproto-test

Try checking out the branch and running this script, which uses virtualenv to install dependencies etc:

cd examples/grpc/python/simple_ecu
./run-betterproto-ecu

Moving over completely to betterproto would take quite some work. Also, we use grpc streaming to client, so a pre-release 2.0 beta of betterproto was required.

All this actually did work in python 3.6.