Implements rendering strategy for tree like components.
|getItemNode||returns HTML element of the item|
|render||renders the specified item or the whole component|
|onAfterRender||occurs immediately after the component has been rendered|
|onBeforeRender||occurs immediately before the component has been rendered|
|onItemRender||for each item rendering, occurs only for items with custom templates|
|onPartialRender||called when part of tree is repainted|