Hide the iAd banner if it is not visible

[rskokan]

If the user navigates from a screen of content with a banner view to a screen that does not have a banner view, and you expect them to be on that screen for a long period of time, remove the banner view from the view hierarchy, set its delegate to nil and release it before transitioning to the new screen of content. More generally, avoid keeping a banner view around when it is invisible to the user.