/**
* add a sublist (nlobjSubList) to this form and return it.
*
* @param {string} name sublist name
* @param {string} type sublist type: inlineeditor|editor|list|staticlist
* @param {string} label sublist label
* @param {string} [tab] parent tab that this sublist lives on. If empty, it is added to the main tab
* @return {nlobjSubList}
*
* @since 2008.2
*/