Document that QGraphicsItemGroup::addToGroup(QGraphicsItem *item) also adds the children of the item to the group

The documentation for addToGroup() should inform that when adding an item to a group, then its children will also be added to the group

http://doc.qt.nokia.com/4.7/qgraphicsitemgroup.html#addToGroup

See the thread at:

http://developer.qt.nokia.com/forums/viewthread/6653/