[AspNetCore] Add Swagger default version support

[kdcllc]

At this time swagger extension method when enabled in the web projects doesn't select a default version for swagger ui.

https://github.com/microsoft/aspnet-api-versioning/blob/master/samples/aspnetcore/SwaggerSample/SwaggerDefaultValues.cs

[ApiVersionNeutral]
[Route("api/optout")]
public class OptOutControler : Controller
{
	[HttpGet]
	public string Get() => HttpContext.GetRequestedApiVersion().ToString();
}