Example configs for Beam on Flink kubernetes operator

The Flink project is working on an official Kubernetes operator. There have been several Flink Kubernetes operator implementations in the past, but having one tied to the Flink project is a good opportunity for Beam to offer a standard deployment solution.

We'd want to get wordcount to work in both Java and Python, and then publish the configs as a template users can modify for their own use cases. Similar to what we did for the GCP Flink operator: https://github.com/GoogleCloudPlatform/flink-on-k8s-operator/blob/master/docs/beam_guide.md