[TIMOB-15576]iOS: adding support for iOS 7 64bit iPad sim

__TESTING INSTRUCTIONS__
Code Review of the ios-sim project to be done on https://github.com/appcelerator/ios-sim/pull/6

the testing can be done only through CLI. 

 * Go to any Titanium app folder in terminal or create a new app.
 * "ti build -p ios -Y ipad -S 7.0 --retina --sim-64bit"
 * Kill the ios simulator app. 
 * "ti build -p ios -Y iphone -S 7.0 --retina --tall --sim-64bit"
 * Kill the ios simulator app. 
 

**Make sure to kill the simulator before running the next command. Otherwise the right simulator will not be displayed**