TreeUtil = function (nodeIdField, childrenField) {
			this.nodeIdField = nodeIdField;
			this.childrenField = childrenField;
			this.memoizedIndex = [];
		}
For the class to work, it needs to know what some information about the structure of the tree
@param nodeIdField - what is the name of the field that holds the unique identifier of the node
@param childrenField - what is the name of the field that holds the array with children for this node
@constructor