Coinbase Book Exception

[timolson]

When Coinbase is enabled in cointrader.properties, you get an exception from the XChange adapter about the service being unimplemented. Coinbase doesn't supply an order book since they are a market maker.

One way to resolve this is to mock an order book with one bid and one ask, at Coinbase's stated price, with the useraccount's trade limit as the volume. We should be able to get that information from the XChange class CoinbaseAccountServiceRaw

We should also have better configuration in the xchange properties to configure xchange queries. Look at the inner class XchangeData.FetchTradesRunnable.run() method, which gets called whenever a query is available from the RateLimiter.