Fixed implementation of path alias settings.

Now report an error if path is already aliased to another location.

modules/node/cms_node_api.e

@@ -182,7 +182,7 @@ feature -- URL
 		require
 			a_node.has_id
 		do
-			create Result.make (a_node.title, cms_api.path_alias (node_path (a_node)))
+			create Result.make (a_node.title, cms_api.location_alias (node_path (a_node)))
 		end
 
 	node_path (a_node: CMS_NODE): STRING