onnxruntime

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>