[TIMOB-14617] iOS 7 : Backgrounding Features


Introduces following new TI.App level Events 

* backgroundfetch
* silentpush
* backgroundtransfer

New Ti.App.iOS level Events

* downloadprogress
* uploadprogress
* downloadcompleted
* sessioneventscompleted
* sessioncompleted

New Ti.App.iOS methods

* setMinimumBackgroundFetchInterval(fetchinterval);
* endBackgroundHandler(<sesionId from the Ti.App events>);

__NOTE: Only do CR for now__

__NOTE: Will include testing instructions and documentation shortly.__