* Major refactor of tree view to support external linking.
* Item update and selection change are now mostly handled by timer for
performance improvement.
* Major change to drag and drop for better support of switching between
copy, move and replace action, and auto adjustment of placement and
relative link.
* Add second column for user changable object description.
* Unified tree view options and action into command group
Std_TreeViewActions.
* Modified object search function to find external objects using
Expression syntax.
