Enables live collection updating while scrolling in touch.  The touch scroll view doesn't update the vertical and horizontal scroll offsets until the touch ends, which means that the clippingFrame of the content won't update until the scroll comes to a stop.  This brings over and tidies the code in CollectionFastPath that uses the touch offset to determine the current clippingFrame and reloads the views while dragging touches.

This also deprecates willReload and didReload on SC.CollectionView because the view itself already handles all the item view and layer pooling.