+2013-12-15: Separated calls for requesting account and portfolio updates.
+2013-12-08: Simplified the record of a 'Contract_details' response.
+ * Commission_report -> Commission
+ * Execution_report -> Execution
+2013-12-01: Removed the client module and its corresponding interface.
+ Module renaming: Contract_specs -> Contract_details
+2013-11-27: Fixed problem with ambiguous contract description.
+ Removed delay of pickler/unpickler construction, because of
+ * no significant reduction in memory footprint
2013-11-25: Delayed pickler/unpickler construction.
2013-11-23: Fixed parse error by extending the Exchange type with a new