Naming was inconsistent and some messages were reused, sometimes with
useless fields. Follow the grpc/protobuf best practice of naming input
and output protobuf message after the RPC function:
MyFunction() will take MyFunctionRequest() and return MyFunctionReply()
A couple of exceptions are made in cases where it does makes sense to
reuse a message (for listdir() like functions)
Change-Id: I5063cef634e2de80934c75aebed5707b1683d5d5
dd8e3a69c8