Maintaining enhanced elements

If an element has a layout handler for its role it is maintained. If an element has a layouter it is maintained. If an element has a laidout it is maintained.

Maintained elements are discarded automatically if they are removed from the DOM. This check is done 3 times per second.

If the active layout is switched the elements in that area are laid out during the next refresh.

Laidout.layout is called if the element is flagged to be laid out during maintenance.