iOS: Updates for GridView
Use attribute to define tests, instead of manually setting them
- Remove ImageViewFormSection as it is unknown/unclear what this is supposed to test
- Add Platform.Supports(Type) for easier programmatic way to determine type supportability
- Add handler attribute to Mouse and MessageBox static classes so Platform.Supports<Mouse>() will work.
EnumerationChangedHandler.Count should return 0 when collection is null
Fix tutorial compile error