Identifies components that can be used as "rubber stamps" to paint the cells in a {@link Grid}.
If you need better control, your renderer can also implement {@link RowRendererExt}. If you need better control about generating {@link Group} and{@link Groupfoot}, your renderer can also implement {@link GroupRendererExt}.
In addition, you could also implement {@link RendererCtrl}. For example, starts an transaction, and uses it to render all rows for the same request.
@author tomyeh
@see ListModel
@see Listbox
@see RowRendererExt
@see GroupRendererExt