Add ability to pass in recalculationMode when calling recalculate

[rynpsc]

It would be nice to be able to set the recalculationMode when calling $order->recalculate() to avoid having to first store the current calculation mode, set the new mode and then restore it. It see it working much the same as the ability to set templateMode when rendering a template.

Old

$initialMode = $cart->getRecalculationMode();
$cart->recalculationMode = Order::RECALCULATION_MODE_ADJUSTMENTS_ONLY;
$cart->recalculate();
$cart->recalculationMode = $initialMode;

New

$cart->recalculate(Order::RECALCULATION_MODE_ADJUSTMENTS_ONLY);