Introduce the ability to override the ElementsFactory globally

[vegegoku]

Now from DominoUIConfig the user can do something like the following to change the default way of creating elements

DominoUIConfig.CONFIG.setElementsFactory(new ElementsFactoryDelegate() {
            @Override
            public AnchorElement a() {
                return new AnchorElement(dom.a())
                        .setAttribute("tabindex", "0")
                        .setAttribute("aria-expanded", "true");
            }
        });