Add apache beam to registry and open source

This is the initial commit of the new billing system, rewritten as an Apache
Beam pipeline. This contains a basic end-to-end pipeline as proof of concept,
and boilerplate for GenerateInvoicesAction, which will eventually be our
automated invoice generation endpoint.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=174184171

java/google/registry/billing/BUILD

@@ -0,0 +1,32 @@
+package(
+    default_visibility = ["//visibility:public"],
+)
+
+licenses(["notice"])  # Apache 2.0
+
+java_library(
+    name = "billing",
+    srcs = glob(["*.java"]),
+    deps = [
+        "//java/google/registry/request",
+        "//java/google/registry/request/auth",
+        "@com_google_dagger",
+        "@com_google_guava",
+        "@joda_time",
+        "@org_apache_beam_runners_google_cloud_dataflow_java",
+        "@org_apache_beam_sdks_java_core",
+    ],
+)
+
+java_binary(
+    name = "counter",
+    srcs = ["MinWordCount.java"],
+    main_class = "google.registry.billing.MinWordCount",
+    deps = [
+        "@com_google_dagger",
+        "@com_google_guava",
+        "@joda_time",
+        "@org_apache_beam_runners_google_cloud_dataflow_java",
+        "@org_apache_beam_sdks_java_core",
+    ],
+)