fix(ios): fix duplicate application delegate allocation

[hansemannn]

While debugging the open scene-related bug that push registration did not fire the events properly, I noticed that during the scene integration, the main app router TiApp was instantiated twice, leading to an unpredicated behavior in the call tree.

I fixed the issue by moving out all scene-related delegates into an own class that is only called by the initial scene configuration that calls the related TiApp code via it's Scenes ObjC extension.

I would like to prompt anyone reading this PR to test it properly, as it's (again) a pretty large change to polish the scene integration.

Open Todos:

• Resolve warnings about duplicate selector implementation in TiApp and it's category TiApp (Addons)
• Tested and approved by at least three community members

For the push-related testing, the following snippet will help:

const win = Ti.UI.createWindow({ backgroundColor: 'yellow' });

win.addEventListener('open', registerForPush);
win.open();

function registerForPush() {
	Ti.App.iOS.addEventListener('usernotificationsettings', function eventUserNotificationSettings() {
		Ti.App.iOS.removeEventListener('usernotificationsettings', eventUserNotificationSettings);

		Ti.Network.registerForPushNotifications({
			success: () => {
				console.warn('Successfully registered for push notifications!');
			},
			error: event => {
				console.error('Cannot register for push notifications!', event);
			},
			callback: event => {
				console.warn('Push arrived!');
				console.warn(event.data);
			}
		});
	});

	Ti.App.iOS.registerUserNotificationSettings({
		types: [
			Ti.App.iOS.USER_NOTIFICATION_TYPE_ALERT,
			Ti.App.iOS.USER_NOTIFICATION_TYPE_SOUND,
			Ti.App.iOS.USER_NOTIFICATION_TYPE_BADGE
		]
	});
}