Introduce routes for ErrorController

With the introduction of the new `ErrorController` (e7fe64f), I'm adding the new `MapTopicErrors()` route (4796340), as well as a standard `MapTopicRoute()` for the `Error` root.

The `MapTopicErrors()` configuration will allow routing to `/Error/{statusCode}`, as used by e.g. `UseStatusCodePages()`, while the `MapTopicRoute()` configuration will allow routing to arbitrary pages under `Error`, such as e.g. `/Error/Unauthorized/`.

Author: JeremyCaney

OnTopic.AspNetCore.Mvc.Host/Program.cs

@@ -69,7 +69,10 @@
 /*------------------------------------------------------------------------------------------------------------------------------
 | Configure: MVC
 \-----------------------------------------------------------------------------------------------------------------------------*/
+app.MapTopicErrors("Error");
+app.MapDefaultControllerRoute();
 app.MapTopicRoute("Web");
+app.MapTopicRoute("Error");
 app.MapTopicSitemap();
 app.MapTopicRedirect();
 app.MapControllers();