Adding gRPC apis functionality

[JayKaku]

As there is already a server written for gRPC, gRPC apis (replicating HTTP ones) would be a valuable addition to the suite as a whole. I would like to discuss further on this and contribute. Thanks.

[Rachitmehrotra]

@stefanprodan we need grpc server for our use case is it possible for you to allow him to raise PR.

[stefanprodan]

Sure let's do first version and echo to see how it goes.

[JayKaku]

#322 here is the new PR with 2 commits as you suggested, the issue with the previous one being the git history was very entangled

[stefanprodan]

In #322 we covered the following APIs:

• echo
• version
• panic