Tree Widget : expand-collapse-style attribute does not seems to be used in node element any more

[Vikas Mayur]

I come across this attribute (expandCollapseStyle) in ModelNode class and it
does not seems to be used any more.
I did a search but could not find much except that it is removed from method
renderNodeBegin() in HtmlTreeRenderer in rev 514099.

-            String *expandCollapseStyle* =
UtilFormatOut.checkEmpty(node.getExpandCollapseStyle(), "expandcollapse");
-            expandCollapseLink.setStyle(*expandCollapseStyle*);
-            expandCollapseLink.setImage(expandCollapseImage);


Will appreciate any pointers.

Thank you,
  Vikas