cubicweb-keyword #1151 Provide an editable treeview to edit a keyword hierarchy [open]

Classification schemes are currently hardly editables. It would be nice to be able to display the hierarchy as a tree (this is actually possible with the treeview view) and make this tree editable, that is where each node would be dragged and dropped anywhere, removed or edited.

done in1.9.0
load left2.000
closed by<not specified>