Remove OWin dependency

Removes the use of the OWIN local server and instead uses Fiddler itself to watch for the OAuth token. (Comments out OAuth tests in Class1.cs). This significantly shrinks the overall size of the add-on (~1.2mb to 0.5mb). 

We could probably get down to 20k and running on .NET2 if we change to use Fiddler's HTTP Message objects and JSON and drop the System.NET.* and NewtonSoft JSON stuff. But I have no idea if that's something you'd find desirable.