Enhance fidelity of POST to Collection

[billdodd]

The existing Mockup-Server support for POSTing to an existing Collection is very helpful. But the fidelity could be improved with some relatively simple enhancements:

1. Add Id, Name, @odata.id, and @odata.type properties to the newly created resource
2. Return the new resource in the response body along with an HTTP 201 Created (instead of HTTP 204 No Content)

[mraineri]

Closing; addressed by recent PR