Update object tree if only equivalences were added or removed

When adding OWLEquivalentClasses(:A :B) for which A and B already
appear in the asserted class hierarchy, there was no change
in the model of the tree component because no child or parent
nodes were added or removed. Consequently, the tree component did not
refresh, and the new labels A = B and B = A of the nodes A and B were
truncated.

This commit make sure that the model gets notified about the changes
of the node.

See #910 (comment)

protege-editor-owl/src/main/java/org/protege/editor/owl/model/hierarchy/OWLObjectHierarchyProviderListener.java

@@ -15,8 +15,8 @@
 public interface OWLObjectHierarchyProviderListener<N extends OWLObject> {
 
     /**
-     * Notifies the listener that the parents and or children
-     * of the specified node might have changed.  This is usually
+     * Notifies the listener that the equivalent objects, parents and or
+     * children of the specified node might have changed.  This is usually
      * called in response to an add/remove axiom change.
      */
     public void nodeChanged(N node);

protege-editor-owl/src/main/java/org/protege/editor/owl/ui/tree/OWLObjectTree.java

@@ -283,17 +283,21 @@ public String getToolTipText(MouseEvent event) {
 
     @SuppressWarnings("unchecked")
     private void updateNode(N node) {
-        // This method is called when the parents or children of
-        // a node might have changed.  We handle the following possibilities
+        // This method is called when the node, its parents or children
+        // might have changed.  We handle the following possibilities
         // 1) The node had a child added
         // 2) The node had a child removed
         // If we are displaying the node which had the child added or removed
         // then we update the node
 
         final Set<OWLObjectTreeNode<N>> treeNodes = nodeMap.get(node);
 
-        // The parents/children might have changed
+        // The node/parents/children might have changed
         if (treeNodes != null && !treeNodes.isEmpty()) {
+        	// The node equivalent objects might have changed
+        	// @@TODO: use provider to check if this were the case
+        	treeNodes.forEach(((DefaultTreeModel) getModel())::nodeChanged);
+
             // Remove children that aren't there any more
             Set<N> children = provider.getChildren(node);