Updated iOS Unified API Support

This compiles against the Xamarin.iOS 8.6.x series of Unified API which will be released on January 5th, at which time, all submitted components supporting this version series will be approved for same day support.

We'd like for this component to be built against the current Xamarin.iOS 8.6.x release that is in Alpha/Beta channels, and be submitted to the store.  We will hold publishing it until Jan. 5th.

Please let me know if you would be able to do this, or there are any problems with the proposed changes, thanks!