* Allow account currency to be overridden by the algorithm
* Fix failing unit test
* Address review
- Revert removal of call check in SecurityPortfolioManager.SetAccountCurrency
- Revert changes to unit tests
- IBrokerage.AccountBaseCurrency now defaults to null
- BrokerageSetupHandler will not change the algorithm's account currency if the brokerage returns null, allowing the algorithm to call SetAccountCurrency in Initialize
Stefano Raggi
b2ed398687