Allow dragging dataitem from within visualization panel

[dem108ht]

You can drag dataitem from "Field" panel to "Visualization" panel, but you cannot move a dataitem in Visualization panel to other caterory: For example, if I want to move one item in Axis to Legend, I have to remove it from Axis, and add it to Legend. If dragging the item from Axis to Legend, it would be much straightforward and easier.