Added orientation support when centerViewController is a subclass of UINavigationViewController

Hi,

I have added orientation support when centerViewController is a subclass of UINavigationViewController.
In my project I use a UINavigationViewController for my centerController. Because of that the controller does not receive any rotation changes as I have not subclassed UINavigationController.
When I present a modalViewController on the centerController and want to only rotate this modalViewController, I need to prevent the rotation in the centerViewController.
I have checked the proper behaviour in iOS 5.1 and iOS 6.1. I can't test it on iOS 4.3.

This was the previous call:
[self.centerController preferredInterfaceOrientationForPresentation];

greetings,
Steven