Fix bug ZK-1714: Databinding 1 cannot clear selection item
http://tracker.zkoss.org/browse/ZK-1714
Fix bug ZK-1715: The disabled listitem shall not be selected when use SHIFT + DOWN key with a paging listbox
http://tracker.zkoss.org/browse/ZK-1715
Merge remote-tracking branch 'VincentJian/B65-ZK-1715'