iOS needs reason for location access to be set manually thru Xcode or plist file

If an attempt is made to ask for location permission iOS looks for a `NSLocationAlwaysUsageDescription` / `NSLocationWhenInUseUsageDescription` in `info.plist`. If this isn't set iOS won't ask the user for permission.

This is OK, but preferably MapKit should be able to check if a description exists and if not add a standard description.
