Add license header to documentation files.

git-svn-id: https://svn.apache.org/repos/asf/maven/shared/trunk@1506553 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/src/site/apt/index.apt.vm b/src/site/apt/index.apt.vm
index cac9d55..2daa17d 100644
--- a/src/site/apt/index.apt.vm
+++ b/src/site/apt/index.apt.vm
@@ -6,6 +6,26 @@
  2013-07-24
  -----
 
+ ~~ Licensed to the Apache Software Foundation (ASF) under one
+ ~~ or more contributor license agreements.  See the NOTICE file
+ ~~ distributed with this work for additional information
+ ~~ regarding copyright ownership.  The ASF licenses this file
+ ~~ to you 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.
+
+ ~~ NOTE: For help with the syntax of this file, see:
+ ~~ http://maven.apache.org/doxia/references/apt-format.html
+
 ${project.name}
 
   Classes to manage report plugin executions with Maven 3, through