Simplify protoc install in protobuf generation scripts

[Avasam]

I was hesitant to use something like https://pypi.org/project/protoc-wheel-0/, but then I found https://pypi.org/project/grpcio-tools/ to run protoc.

This simplifies the protoc installation logic by installing the protoc executable from PyPI (using an official source) rather than downloading and unzipping a platform-specific zipped distribution from GitHub.

I also added the protoc (aka libprotoc) version to the extra-description. And wrapped the long description string.

Its also one step closer to running the scripts directly in Windows (using Git bash), I think all I'd need to add is a python vs python3 condition.

[srittau]

I don't claim to understand what's going on here, but I'm sure you know what you're doing.

[Avasam]

@srittau I've updated the description to be a bit more clear about what I'm doing here.