Expose events for the Items reorder API

Images loaded from memory stream behave strange - on iOS they don’t load immediately, only after list is scrolled and after that they start resizing and reordering randomly when scrolling; on UWP they load on initialization but have same problem with reordering.

Investigate the options for exposing API for controlling the scroll position of the ListView.

The feature can be implemented on the different platforms through custom renderers:

Android: http://docs.telerik.com/devtools/android/AndroidControlsDoc/com/telerik/widget/list/RadListView.html#scrollToPosition(int)

iOS: http://docs.telerik.com/devtools/ios/api/Classes/TKListView.html#//api/name/scrollToItemAtIndexPath:atScrollPosition:animated:

UWP: ScrollItemIntoView()

Available in the R1 2018 SP release. More information: https://docs.telerik.com/devtools/xamarin/controls/listview/features/listview-features-scrolling

Add support for GroupKey of ListView to be complex object, allowing to display more complex information in the group headers.

Available in the R2 2018 release.

Add support for expand/collapse functionality for ListView groups.

Available in the R2 2018 release.

Add support for ListView item template selector.

Available in minor release 2017.2.0721. It will also be available in the R3 2017 release.