Investigate support for the server reflection protocol

[njpatel]

‏@louiscryan: @njpatel @grpcio Very cool! You might want to take a look at https://t.co/vQLFqrcxBs and support that at some point

https://github.com/grpc/grpc/blob/master/doc/server-reflection.md

[ttencate]

The official grpc_cli client also supports – even requires – server reflection. Might be useful to look at its code.