Publish "Test Template" Projects for the test-proxy

Right now, we have some `sample usage`, but that is very specifically just console apps that:

- start recording
- run single request
- stop recording
- start playback
- run single request (playback)
- stop

We need to extend these to be actually full test projects for use in production applications.

Currently requested from @xboxeer :

For `.net`:
- [x] Publish an `xunit` and `unit` test project examples that start record/playback in setup function -> run test.

For `go`:
- [x] Consult with @benbp and get the test framework. We'll probably end up ripping the go test framework almost verbatim.