code: public CMFolder addChild( String id, String name )
      {
          CMFolder childFolder = new CMFolder( id, name );
          childFolder.parent = this;
          this.children.put( name, childFolder );
          return childFolder;
      }
docs: Adds a child folder
  
  @param id id of the child folder
  @param name name of the child folder
  @return the added folder