New queue implementation issues

[x] When moving from managed to preferred or vice versa - message should be "...these items.." instead of "these item"
[x] When dragging an item to a list which already holds items, it can only be moved when hovering over the existing ones
[x] When dragging to an empty space, it is added momenterely and flickers back - without the prompt
[x] When dragging to preferred and not placing between existing lines, if placed below all of them, it should be placed last
[x] Preferred icon should be resized to concurrency icon size

kube-HPC / hkube