Move terraform and kubernetes folder to be under proxy (#127)

* Move terraform and kubernetes folder to be under proxy

There is no reason for them to be under proxy/src/... any more now that
we have a Gradle-idiomatic folder structure.

proxy/terraform/modules/gke/variables.tf

@@ -0,0 +1,13 @@
+variable "proxy_service_account_email" {}
+
+variable "proxy_cluster_region" {}
+
+variable "proxy_cluster_zones" {
+  type = "map"
+
+  default = {
+    americas = "us-east4-a"
+    emea     = "europe-west4-b"
+    apac     = "asia-northeast1-c"
+  }
+}