support grpc in parser about froto HOT 3 CLOSED

gRPC made it to 1.0 a couple of days ago.
https://cloudplatform.googleblog.com/2016/08/gRPC-a-true-Internet-scale-RPC-framework-is-now-1-and-ready-for-production-deployments.html

from froto.

The service and rpc keywords are both supported, as is the option keyword.

However, looks like the parser has several bugs:

• The option keyword on rpc is failing to parse correctly for a number of reasons, including that several parsers are missing the option literal and are otherwise broken
• The option syntax currently does not support the "optional" option syntax which handles inner curly braces and ":" rather than "="
• Custom options with dots must be completely surrounded by parens, but this should only be needed on the top-level portion of the name; e.g., (my).custom.option.

There may be other issues in here, as well...

from froto.

Thanks for the analysis @jhugard!

from froto.