Add Desktop Support

Unfortunately the solution/project got upgraded to Visual 2012 as that is all I have. If you don't want to make this move hopefully you can merge the change I've made in with the VS2010 solution/project files.

I've added a Sample console app to the solution to show how the library can be used for desktop apps.

The workflow is 

1) Get your AuthTokenUrl as usual.
2) The client would then need to launch a browser to that URL allowing the user to allow the application and get they're pin. 
3) They enter the pin into the application and it calls the new method in the Authenticator class called GetAuthCredentialFromPin which returns the AuthCrential object as usual for them to make calls with.

I suppose the library could open the browser but I thought this would be better in the client so the developer can choose how they want to handle this.