Split Out CommandLineParser to it's own library

[aef123]

I've been using TestApi for years now. Solely for the CommandLineParser classes. I use it for any command line utility I build.

I'd love to have this functionality split out to it's own NuGet package. And possibly it's own project altogether so I don't have to take in all the testing stuff I don't need (like WPF Visual Verification) just for the command parsing functionality.

I've considered doing this fork myself, but would rather it be done officially so we don't get feature drift.