Add support for binary authorization in GKE (hashicorp#1884)

* revendor container/v1beta1

* add support for binauthz in gke

* update description

Author: danawillow

docs/r/container_cluster.html.markdown

@@ -92,6 +92,9 @@ output "cluster_ca_certificate" {
 
 * `description` - (Optional) Description of the cluster.
 
+* `enable_binary_authorization` - (Optional) Enable Binary Authorization for this cluster.
+    If enabled, all container images will be validated by Google Binary Authorization.
+
 * `enable_kubernetes_alpha` - (Optional) Whether to enable Kubernetes Alpha features for
     this cluster. Note that when this option is enabled, the cluster cannot be upgraded
     and will be automatically deleted after 30 days.