Implement initial set-up for the health checking service

[clintonpi]

Motivation:

This setup is needed as part of the implementation of the health checking service.

Modifications:

• Pull in updates for the upstream protos and re-generate stubs.
• Update the Protos/fetch.sh script to copy over grpc-proto/grpc/health/v1/health.proto and generate the health checking stubs.
• Update the Protos/generate.sh script to generate the health checking service and messages for v2 and only the server.
• Add a target to the package manifest called GRPCHealth.

Result:

The stubs for the health checking service are now available.