Switch to MIT License

[rajsite]

It was approved to update the license for VireoSDK to the MIT License.

With some (mostly in person) discussion with the open source guild the following was deemed reasonable to enable the transition in this PR:

• Replace the contents of License.txt with the MIT License text
• Update the npm package and nuget package license fields as needed
• Update license references in README and docs (as opposed to the license of the doc themselves)
• Add / update the license header in all source files:
  • Source code (.cpp .h .js .via .java .g4 *.php)
  • Infrastructure files (Makefiles .yml .sh .gyp .bat *.xml)
  • Docs (*.md) - The license for the documentation itself

And we can use an SPDX ID for the header. The following is the header with a short identifier:

// Copyright (c) 2020 National Instruments
// SPDX-License-Identifier: MIT

In addition, a note about SPDX usage was added in the license file as discussed on page 14 of Using SPDX License List “short identifiers” in source files.

I'll not be adding the header to "data files" (.json .vtr), IDE config files (for XCode, Visual Studio), or via files that are part of the "vtr test suite" located in /test-it/ViaTests (as there are tests for parsing via itself where line number reporting is significant). The open source guild said this was fine, primarily wanting to ensure the root License file update.

Fixes #28

[sanmut]

Thanks for all the hard-work fixing issue #28 !!!

[rajsite]

Note: Do not merge yet, pending a discussion on adding a THIRDPARTY.txt file.

[rajsite]

Note: Do not merge yet, pending a discussion on adding a THIRDPARTY.txt file.

Got feedback that adding a THIRDPARTY.txt for use in distributions works, can merge when ready