More updates for Unified API following the breaking changes in Xamarin.iOS 8.6.
Merge remote-tracking branch 'upstream/3.5' into 3.5
Merge remote-tracking branch 'upstream/3.5' into 3.5

Conflicts:
	CrossUI/CrossUI.Touch/Dialog/Elements/DateTimeElement.cs
	CrossUI/CrossUI.Touch/Dialog/Elements/MessageSummaryView.cs