This class provides for a checkout experience when used in conjunction with the Restricted flag on an object.

If an avatar is in possession of any objects with the Restricted flag set, clicking “Checkout” on an item of this classs will list those objects, and give an option to pay the total of their salePrices, at which point the Restricted flags will be cleared.

Field 'serviceCharge' is a %age amount that will be added to a bill, e.g. '5' will charge an extra 5%.