add cron registration status updates for iOS devices

[mwfarb]

It would be good to query APNS for accurate registered/unregistered status and provide that feedback to the sender if using an unregistered device and there is no new registration id in our registration table. Perhaps this could be done daily.

[tenmalin]

According to APNS service, it provides feedback from the default feedback server. The feedback contains timestamps indicating when the app has no long existed on the device (uninstallation time).

See
https://developer.apple.com/library/mac/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/Chapters/CommunicatingWIthAPS.html#//apple_ref/doc/uid/TP40008194-CH101-SW3