dotnet test adapter

[mausch]

After #50 , implement the adapter for dotnet test to work.

Docs are currently dismal so I guess we'd have to dive into xunit or nunit's code.

[idg10]

A related but different issue is that there didn't seem to be any support for non-core adapters (i.e., the kind of adapter that has been around for years, used outside of .NET Core project).

So I rustled one up: https://github.com/interactsw/fuchu-adapter