New datasource: google_container_cluster (hashicorp#740)

* Add google_kubernetes_cluster datasource

Add documentation for google_kubernetes_cluster datasource

Rename datasource to google_container_cluster

To be consistent with the equivalent resource.

Rename datasource in docs.
google_kubernetes_cluster -> google_container_cluster.
Also add reference in google.erb file.

WIP

Datasource read needs to set an ID, then call resource read func

Add additional cluster attributes to datasource schema

* Generate datasource schema from resource

Datasource documentation also updated.

* add test for datasourceSchemaFromResourceSchema

* Code review changes

Author: sl1pm4t

docs/d/datasource_container_cluster.html.markdown

@@ -0,0 +1,61 @@
+---
+layout: "google"
+page_title: "Google: google_container_cluster"
+sidebar_current: "docs-google-datasource-container-cluster"
+description: |-
+  Get info about a Google Kubernetes cluster.
+---
+
+# google\_container\_cluster
+
+Get info about a cluster within GKE from its name and zone.
+
+## Example Usage
+
+```tf
+data "google_container_cluster" "my_cluster" {
+  name   = "my-cluster"
+  zone   = "us-east1-a"
+}
+
+output "cluster_username" {
+  value = "${data.google_container_cluster.my_cluster.master_auth.0.username}"
+}
+
+output "cluster_password" {
+  value = "${data.google_container_cluster.my_cluster.master_auth.0.password}"
+}
+
+output "endpoint" {
+  value = "${data.google_container_cluster.my_cluster.endpoint}"
+}
+
+output "instance_group_urls" {
+  value = "${data.google_container_cluster.my_cluster.instance_group_urls}"
+}
+
+output "node_config" {
+  value = "${data.google_container_cluster.my_cluster.node_config}"
+}
+
+output "node_pools" {
+  value = "${data.google_container_cluster.my_cluster.node_pool}"
+}
+```
+
+## Argument Reference
+
+The following arguments are supported:
+
+* `name` - The name of the cluster.
+
+* `zone` - The zones this cluster has been created in.
+
+- - -
+
+* `project` - (Optional) The project in which the resource belongs. If it
+    is not provided, the provider project is used.
+
+## Attributes Reference
+
+See [google_container_cluster](https://www.terraform.io/docs/providers/google/r/container_cluster.html) resource for details of the available attributes.

google.erb

@@ -43,6 +43,9 @@
       <li<%= sidebar_current("docs-google-datasource-compute-lb-ip-ranges") %>>
       <a href="/docs/providers/google/d/datasource_compute_lb_ip_ranges.html">google_compute_lb_ip_ranges</a>
       </li>
+      <li<%= sidebar_current("docs-google-datasource-container-cluster") %>>
+      <a href="/docs/providers/google/d/google_container_cluster.html">google_container_cluster</a>
+      </li>
       <li<%= sidebar_current("docs-google-datasource-container-versions") %>>
       <a href="/docs/providers/google/d/google_container_engine_versions.html">google_container_engine_versions</a>
       </li>