Update the license header for every source file, as well as the documentation.

Fixes #1209
diff --git a/docs/conf.py b/docs/conf.py
index 4ed2caf..b70114d 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -1,17 +1,8 @@
 # -*- coding: utf-8 -*-
 
-# 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.
+# This file is dual licensed under the terms of the Apache License, Version
+# 2.0, and the BSD License. See the LICENSE file in the root of this repository
+# for complete details.
 
 #
 # Cryptography documentation build configuration file, created by
diff --git a/docs/cryptography-docs.py b/docs/cryptography-docs.py
index e4e9296..6aa7847 100644
--- a/docs/cryptography-docs.py
+++ b/docs/cryptography-docs.py
@@ -1,15 +1,6 @@
-# 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.
+# This file is dual licensed under the terms of the Apache License, Version
+# 2.0, and the BSD License. See the LICENSE file in the root of this repository
+# for complete details.
 
 from __future__ import absolute_import, division, print_function
 
diff --git a/docs/development/custom-vectors/cast5/generate_cast5.py b/docs/development/custom-vectors/cast5/generate_cast5.py
index 6a4acda..20f3517 100644
--- a/docs/development/custom-vectors/cast5/generate_cast5.py
+++ b/docs/development/custom-vectors/cast5/generate_cast5.py
@@ -1,15 +1,6 @@
-# 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.
+# This file is dual licensed under the terms of the Apache License, Version
+# 2.0, and the BSD License. See the LICENSE file in the root of this repository
+# for complete details.
 
 from __future__ import absolute_import, division, print_function
 
diff --git a/docs/development/submitting-patches.rst b/docs/development/submitting-patches.rst
index 54005d2..ff650c4 100644
--- a/docs/development/submitting-patches.rst
+++ b/docs/development/submitting-patches.rst
@@ -25,7 +25,14 @@
 
 `Write comments as complete sentences.`_
 
-Every code file must start with the boilerplate notice of the Apache License.
+Every code file must start with the boilerplate licensing notice:
+
+.. code-block:: python
+
+    # This file is dual licensed under the terms of the Apache License, Version
+    # 2.0, and the BSD License. See the LICENSE file in the root of this repository
+    # for complete details.
+
 Additionally, every Python code file must contain
 
 .. code-block:: python