Support triggering GC for one project via REST

The Git garbage collection for one project can now be triggered by
POST on '/projects/*/gc'.

Change-Id: I6d45f33196f3f356648c817d9a2d8465de49bb5c
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/restapi/StreamingResponse.java

@@ -0,0 +1,23 @@
+// Copyright (C) 2013 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.restapi;
+
+import java.io.IOException;
+import java.io.OutputStream;
+
+public interface StreamingResponse {
+  public String getContentType();
+  public void stream(OutputStream out) throws IOException;
+}