PR #307 provides a way to get a string in the following format "gcloud-java/xxxx" (xxxx stands for the version) from the service options. We should set it for every service.

The typical way to set it for apiary clients is via setApplicationName on the apiary service builder.

When #300 is fixed that should be simple as we will have access directly to the apiary (or gRPC) client
though it would be nice a way to specify it even before that.

For more info see #278