[TIMOB-17894] iOS: Support Apple's integration of TestFlight beta testing

As described in [this blog on tiDev.io](http://www.tidev.io/2014/10/16/how-to-use-apples-new-testflight-beta-testing/) it currently takes a manual step to make an dist-appstore build compatible for distribution via Apple's integration of TestFlight. Nick also found out that the entitlement can't be left in Reading the "Submit to App Store" section in Apple's [guide on TestFlight Beta Testing](https://developer.apple.com/library/ios/documentation/LanguagesUtilities/Conceptual/iTunesConnect_Guide/Chapters/BetaTestingTheApp.html) it looks like you can leave the new entitlements in and use the same build to publish to the App Store: {quote} When you are done using TestFlight Beta Testing, you can submit the app for final review. Before you submit it, make sure you no longer want to test it or any builds you uploaded earlier than it. When the app becomes Ready for Sale in the App Store, testing automatically stops on earlier builds, and you will be unable to view or test them. {quote} So it looks like the tooling can simply be adjusted to add the new entitlement for any --dist-appstore builds.