Fixed: CPDatePicker value is wrong when making a click on the stepper

Previously, when making a click on the stepper of a textual CPDatePicker, the intern value of the stepper wasn't updated with the correct value of the CPDatePicker. 
This occurred when the user changed the dateValue in the delegate methods of the textField or when the user changed the value by clicking on the stepper
Change the comment to:

// Before sure to update the stepper value. We don't use -setObjectValue to avoid a binding update.