Nested itemconverter for recursive arrays.

We ran into an issue where we can a data structure similar to  below

	$mappings = array(
		'OrderNo' => 'order_number',
		'Total'   => 'order_total',
		'OrderedProducts' => 
			array(
				array (
					'ProductId  => 'sku',
					'Qty'	    => 'quantity',
					'LineTotal' => 'line_total'					
				)
			)
	);
	
The `MappingItemConverter` only could cope with none nested arrays.