“The rule of equity which insists on those who by use of a fiduciary position make a profit, being liable to account for that profit, in no way depends on fraud, or absence of "bona fides"; or upon questions or considerations as whether the property would or should otherwise have gone to the plaintiff, or whether he took a risk or acted as he did for the benefit of the plaintiff, or whether the plaintiff has in fact been damaged or benefited by his action. The liability arises from the mere fact of a profit having, in the stated circumstances, been made.”