Fixed notifications queue + compilation warning

- when showWithStatus was called while another notification was being shown, it was wrongly changing its icon to spinner and when the first action was finished, the new action would not see its status set correctly. showWithStatus and showImage now share the same behaviour: they add the action to the queue (or modify its status if already exists) then if the action is primary show it, otherwise return. That action will then be later picked up if it is still running.

- the animationDuration variable in positionBar was used without ever being initialised. It is now set to some default value.