Considering using google-auth-library-java for auth

We were told that there is a newer auth library: [google-auth-library-java](https://github.com/google/google-auth-library-java). It supports, e.g., [gRPC](http://www.grpc.io/about/).

However, we would not be able to completely get away from [google-oauth-java-client](https://github.com/google/google-oauth-java-client), because we are very much interested in using `LocalServerReceiver` it provides.