* 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
