Add NotFoundHandler.CreateCustomNotFoundController

You can configure your own controller in Global.asax
NotFoundMvc.NotFoundHandler.CreateCustomNotFoundController =
requestContext =>
{
//some sort of logic...
return new MyCustomNotFoundController(requestContext);
//or return null for default functionality
}
Refactor controller creation

Renamed NotFoundHandler.CreateCustomNotFoundController to
NotFoundHandler.CreateNotFoundController.

Also changed the code to always use this delegate to create the
controller, defaulting to NotFoundController.
Update sample project VS version
v1.2.0
Update nuget and fix build