Add self-check for api/status after the WebHost has been started

[michaelschnyder]

The WebHost should try to connect to himself in order to make sure the HttpListener has been able to register all the http prefixes and the API is available at the specified route.

This is easy for simple registrations like "http://localhost:80" but we probably need some more logic to also test registrations in the format http://0:0:0:0:80 or http://*:80. See: https://msdn.microsoft.com/en-us/library/system.net.httplistener(v=vs.110).

To connect back to the API, the Client Library of WebAPI could be used (probably needs additional IL-Merging) or the default TCP Stack from .NET