feat(charts): Add support for gRPC backends.

feat(charts): Add support for gRPC backends.

The Helm Chart is still a fast changing target. This MR contains the following changes:

• Support for (non-public) gRPC services. The public load balancer does not yet support routing gRPC.
  • Enable Istio injection for the entire service namespace.
  • Rename the backend protocol to "http" (from "rest"). This is an Istio requirement for named ports.
• Expose the resources field to users so they can configure arbitrary resources (e.g. ephemeral-storage) as well as resource requests and limits.
• Support user-defined environment variables.
• Remove the monitoring port (8082) that was exposed as /varz – this is specific to the example-service.

Issue: Add the ability to generate Kubernetes configur... (team#286)