InstallPlugin: Move static Input class to separate class in API

Change-Id: I9fa66829addde23feaf089be39d1f2285fe8006e

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/common/InstallPluginInfo.java

@@ -0,0 +1,23 @@
+// Copyright (C) 2017 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.common;
+
+import com.google.gerrit.extensions.restapi.DefaultInput;
+import com.google.gerrit.extensions.restapi.RawInput;
+
+public class InstallPluginInfo {
+  public @DefaultInput String url;
+  public RawInput raw;
+}