ellipse trajectory for rotary mode using a new radiusZ property. 

This change is 100% backward compatible. It lets people adjust the shape of the circle for rotary mode into an ellipse. it's useful for when you want to show the items in the back a little closer to the front items without affecting item spacing.
"radiusZ" default is equal to "radius".

The "iCarouselOptionsDemo" example project has been modified to exhibit the feature.