Adding a message handler for the version check message. Also introduced an IDotnetTest that handles state and handlers (the state machine).
Adding the test discover start message handler and introducing a test runner.
Added the handler for the GetTestRunnerProcessInfo message. Also, modified dotnet test to have separate setter for the special message handlers for terminate and unknown messages and added a separate method to add new reporting channels to DotnetTest, so that it can handle the new listener for the test runner.
Added the test runner test discovery handlers.
Added handlers to deal with the test execution itself.
Updated dotnet-test program to use the message handlers during design time.
Added a test for the whole discover tests message flow.
Added a test for the run tests full message exchange.
