Use kustomize and envsubst to generalize k8s config.

Adds a [kustomize](https://github.com/kubernetes-sigs/kustomize) overlay
for a new staging environment. Additionally, adds environment variables
in the place of certain pieces of information that need to be templated.

The K8s README ("deploy/README.md") has been updated to reflect the new
method for applying config.

This commit also removes the configuration for the AWS cluster and
references to AWS in the README.

deploy/azure/crls-sync.yaml

@@ -12,7 +12,7 @@ spec:
           restartPolicy: OnFailure
           containers:
           - name: crls
-            image: pwatat.azurecr.io/atat:latest
+            image: $CONTAINER_IMAGE
             command: [
               "/bin/sh", "-c"
             ]