Account.FieldName: Move to extension API as AccountFieldName

Change-Id: I103dbe8bfaeb2acc67c6afd505c693953860bb0c

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/client/AccountFieldName.java

@@ -0,0 +1,19 @@
+// Copyright (C) 2016 The Android Open Source Project
+//
+// 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 com.google.gerrit.extensions.client;
+
+public enum AccountFieldName {
+  FULL_NAME, USER_NAME, REGISTER_NEW_EMAIL
+}