gRPC and protocol buffer support

Hi all contributors, do you have any plan to :
- add gRPC support (over HTTP2) for external API
- use protocol buffer to define external API (and so generate REST API + swagger definition) using protoc

https://coreos.com/blog/grpc-protobufs-swagger.html

The issue names no files, tests, or entry points. Begin by locating the current external API and its REST and Swagger definition setup, then assess the requested gRPC over HTTP/2 and protocol-buffer generation work. Done would require an agreed implementation scope and support for the proposed external API definitions.

Written by the indexing model from the issue text.