swift create uinavigationcontroller programmatically
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
self.window = UIWindow(frame: UIScreen.mainScreen().bounds)
var nav1 = UINavigationController()
var mainView = ViewController(nibName: nil, bundle: nil) //ViewController = Name of your controller
nav1.viewControllers = [mainView]
self.window!.rootViewController = nav1
self.window?.makeKeyAndVisible()
}