Enable transitions for add/move/remove operations on views

ListView and GridView currently do not have built-in support for transitions when items are added to, removed from, or moved within the view. It is possible to use the onAdd and onRemove signal handlers to animate an item from or to a specific position when it is added or removed; however, it is not easy to implement more complex effects, such as animating neighbouring items when an item is added or removed. Also, it's not possible to animate items when they are repositioned following a move() operation on the underlying model.

Supporting such transitions enables developers to easily create more dynamic views that animate and shuffle themselves as items are added, moved and removed. Also, the feature should support a level of control over how different items can be animated; for example, when an item is moved within a view, it should be possible to animate the moved item in a different manner to other items that are displaced as a result of the move.

With this feature, it should be easy to produce the various transitions demonstrated in the attached QML files.

(The Row, Column and Grid elements currently have basic transition support for add and remove operations. This should be expanded in line with the new transitions for ListView and GridView so that they all have the same capabilities.)