PickList: Add dragdrop support

[Xerphis]

I'm submitting a ... (check one with "x")

[ ] bug report
[x ] feature request
[ ] support request => Please do not submit support request here, instead see https://forum.primefaces.org/viewforum.php?f=57

Currently, you need to use the arrow button to move items between lists. It would be very convenient to move items using the "drag&drop" method as the optional prop "dragdrop", like in the "OrderList" component.