Translation layer and dotnet test --designtime

[codito]

TranslationLayer currently supports interaction with vstest.console directly. It needs to support interaction with dotnet test:

• User should be able to provide path to dotnet.exe
• If path to dotnet.exe is not provided, it should pick up the executable from PATH environment variable
• TranslationLayer should be published as a public nuget package

[codito]

First draft is checked in #306