Delete license headers from files

Summary:
This commit doesn't change license of any file. It just makes the license implicit (inherited from LICENSE file in the root directory).

We are removing the headers for these reasons:

- It wastes space in editors, less code is visible in editor upon opening a file.
- It brings noise to diff of the first change of any file every year.
- It confuses Git file copy detection when creating small files.
- We don't have an explicit license header in other files (JS, CSS, images, documentation).
- Using license header in every file is not obligatory: http://www.apache.org/dev/apply-license.html#new.

This change is approved by Alma Chao (Lead Open Source and IP Counsel at Facebook).

Test Plan: Verified that the license survived only in LICENSE file and that it didn't modify externals.

Reviewers: epriestley, davidrecordon

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2035

Differential Revision: https://secure.phabricator.com/D3886

scripts/repository/reparse_all_commit_messages.php

@@ -1,22 +1,6 @@
 #!/usr/bin/env php
 <?php
 
-/*
- * Copyright 2011 Facebook, Inc.
- *
- * 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.
- */
-
 echo "This script is obsolete. Instead, use:\n\n".
      "  $ reparse.php --all <repository_name> --message\n\n".
      "See that script for more options.\n";