OpenTimelineIO License & CLA Change (#1285)

* Updated both Corporate and Individual CLA
* Switched to standard Apache License, Version 2.0
* Added verify_license.py script to help ensure all source files have the right license header.
* Added SPDX license headers
* Update contributing.md and CONTRIBUTING.md to explain EasyCLA
* Removed mention of ffmpeg_burnins license, which was previously relicensed here: AcademySoftwareFoundation/OpenTimelineIO#679

Signed-off-by: rosborne132 <[email protected]>

Author: jminor

contrib/opentimelineio_contrib/adapters/maya_sequencer.py

@@ -1,26 +1,5 @@
-#
+# SPDX-License-Identifier: Apache-2.0
 # Copyright Contributors to the OpenTimelineIO project
-#
-# Licensed under the Apache License, Version 2.0 (the "Apache License")
-# with the following modification; you may not use this file except in
-# compliance with the Apache License and the following modification to it:
-# Section 6. Trademarks. is deleted and replaced with:
-#
-# 6. Trademarks. This License does not grant permission to use the trade
-#    names, trademarks, service marks, or product names of the Licensor
-#    and its affiliates, except as required to comply with Section 4(c) of
-#    the License and to reproduce the content of the NOTICE file.
-#
-# You may obtain a copy of the Apache License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the Apache License with the above modification is
-# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
-# KIND, either express or implied. See the Apache License for the specific
-# language governing permissions and limitations under the Apache License.
-#
 
 """Maya Sequencer Adapter Harness"""