Add mapper to import domains from RDE deposits

With some additional cleanup by Ben McIlwain.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=146695665

java/google/registry/rde/imports/ResourceExistsException.java

@@ -0,0 +1,23 @@
+// Copyright 2017 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.rde.imports;
+
+/**
+ * Indicates that a resource already exists and was not imported.
+ */
+public class ResourceExistsException extends RuntimeException {
+
+  private static final long serialVersionUID = -9180381693364904061L;
+}