This patch renames it to QQuickItemViewTransitionableItem, and
FxViewItem and PositionedItem now create instances of this instead of
subclassing it, to reduce the memory used when transitions are not
required.

Change-Id: Ie050cda5a121bff9542c7ba7356f6eacf37d241a
Reviewed-by: Alan Alpert <alan.alpert@nokia.com>