iOS: Expose applicationState property of UIApplication Class

Feature

Expose the applicationState property through Titanium API so we can know the application was frontmost when it received a notification.

http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UIApplication_Class/Reference/Reference.html#//apple_ref/occ/instm/UIApplication/applicationState

Customer notes

The applicationState property is not exposed in titanium, thus, there is no way take proper action in response to a remote notification.

Specifically, if the app is in the background and receives a push notification, the notification popup displays, and when the app is launched from the popup, the messageCallback is invoked. There is no way to determine from within this callback whether the system had already displayed the popup to the user.

Associated HD ticket

APP-185982