Adopt iOS 11 Kiosk API

[ashfurrow]

App should ideally lock the home button programmatically using the new Autonomous Single App Mode API. See https://github.com/artsy/eidolon/issues/670 . This may require changes to how we provision our iPad fleet, since the API requires us to use Apple's Mobile Device Management, which might be good for us to adopt anyway. We probably should be using Apple for deployment anyway.