Allow for 'clone' to be returned if value is 'clone'

Fixed issue in toFn causing checkPull and checkPut to always be true when `value == null`

In short, this revamp allows for elements that are parents of the currently hovered element to also autoscroll.

For native DnD, it autoscrolls the parents, but does not autoscroll the hovered element, as this is handled by HTML5.