Add child page support.

- Add support to create a new node as a child of an existing node.
   - Update or add a parent for a given node.
Fix delete and trash behavior: when a node is not published only the
   - author or admin see it.

Fix Node and Page node Revisions.

modules/node/persistence/cms_node_storage_null.e

@@ -86,6 +86,12 @@ feature -- Access: node
 			create {ARRAYED_LIST [CMS_USER]} Result.make (0)
 		end
 
+	available_parents_for_node (a_node: CMS_NODE): LIST [CMS_NODE]
+			-- <Precursor>
+		do
+			create {ARRAYED_LIST [CMS_NODE]} Result.make (0)
+		end
+
 feature -- Node
 
 	new_node (a_node: CMS_NODE)