* @param treemodel
* @param selectableFilter
* @return
*/
public MultipleSelectionElement addTreeMultiselect(String name, String i18nLabel, FormItemContainer formLayout, TreeModel treemodel, INodeFilter selectableFilter){
MultipleSelectionElement mse = new MultiSelectionTree(name, treemodel, selectableFilter);
setLabelIfNotNull(i18nLabel, mse);
formLayout.add(mse);
return mse;
}