Add gRPC/protobuf3 support.

[aloiscochard]

It's actually purely config, but that would be nice to have some facilities, I suppose we could get java_rpc_out and plugin value generated behind a gRPC flag or something.

Here is the hacked config I have in my toy project at the moment:

      version in protobufConfig := "3.0.0-alpha-3.1",
      protocOptions in protobufConfig ++= Seq(
        "--plugin=protoc-gen-java_rpc=/usr/local/bin/protoc-gen-grpc-java",
        "--java_rpc_out=examples/target/scala-2.11/src_managed/main/compiled_protobuf"
      )

What do you think?

[xuwei-k]

FYI

• https://github.com/trueaccord/ScalaPB/issues/44
• https://github.com/xuwei-k/grpc-scala-sample

[ghost]

@aloiscochard can this be modified to use grpc jar from repo instead of local binary?

[eed3si9n]

Here's my PR for this - https://github.com/sbt/sbt-protobuf/pull/177