Remove DisplayQty from CreateSimpleLimit

[Diegoboca]

I created a new method CreateSimpleLimitIceberg in order to create a new order with a defined displayed quantity. I remove the field displayQty from the object used in the method CreateSimpleLimit. I think it is correct to not send the field displayQty when we want to create a simple limit order, because if you try to amend an order with a defined displayQty it becomes an Iceberg order.