Create an order book contract for the exchange contract family

[cmickeyb]

An order book is typically used to match buyers and sellers. I can imagine an order book for the exchange contract family that would store exchange/order contract pointers and/or auction pointers. The order book would be a place where exchange opportunities could be discovered.

Some potential ideas for the order book:

• The order book is a list of open exchange contracts; it should include all of the information necessary for a buyer to discover and interact with the order which may include all of the contract files (*.pdo) and all of the context files.
• Listing an order may require that the seller include a deposit with the order book in order to ensure that those sellers continue to maintain the order book; that is, I can imagine that an order added to the order book would have a limited duration after which the deposit is forfeited to the order book. This is really about ensuring that information in the order book is not stale.