Datasource classes made public.
Updated ibcsharp client.
Changes to IB class to make it testable.
Added handling of error replies to historical data requests.
Started writing tests for the IB class.
Added reference to IB client library to test project.
Minor cleaning up.
Added a test for the sending of error replies when the broker throws an
exception from a historical data request.
Wrote a few more tests for the HistoricalDataBroker.
HistoricalDataServer now sends an error reply when something goes wrong
in a historical data request.
HistoricalDataBroker now checks that a data source exists and is
connected before trying to get data from it.