Outstanding order list and trade list protocol command implementation

[analyticbastard]

We need two new request commands in the protocol for a given trading desk (broker-id):

• list outstanding orders in the engine
• list completed trades in the connector (query the database)

To prevent engine overload with possible outstanding order request, connectors could cache this outstanding order list by:

• Querying the engine for the whole book upon startup
• Insert new order into list upon new order received from trading desk
• Remove orders from this list upon engine match event

[analyticbastard]

Completed protocol with commit 887cd7a