Enable .NET Core 2.0 and .NET Framework 4.6.1 in Microsoft.AI.MachineLearning NuGet package (#4125)
* add project to download cswinrt and build winrt c# interop dll
* Add to nuget package
* reverse if check
* run generation before core compile
* add generated files to compile
* update .net package to binplace native libs
* add props to .netstandard2.0 folder
* auto binplace ml native binaries
* force 'Any CPU' platform build
* Fix anycpu and platform targets
* fix flake errors
* fix variable order
* fix flake pep8 errors, semicolon
Co-authored-by: Sheil Kumar <sheilk@microsoft.com>