Protocol Buffer code generation (#1635)

Dear Dusan,

Let me suggest to add protocol buffer code generation support.

This is intermediate data structure description format which is transpiled to target languages (C#, Java etc.). It's main purpose is to transport data between systems.

It is widly used in the industry - and has 41k stars on GitHub [1]. I also added a short review that details it's relevance [2].

References:

- https://developers.google.com/protocol-buffers

- https://developers.google.com/protocol-buffers/docs/proto3

- [1] https://github.com/protocolbuffers/protobuf

- [2] https://codeclimate.com/blog/choose-protocol-buffers/

Thanks a lot for reviewing my suggestion.