Via nfarina/calloutview#84, SMCalloutView is now accessible. Activating a focused annotation now shows its callout view and focuses its left accessory view, if present, or the title view. There is a “return to map” accessibility element for dismissing the callout view and restoring focus to the annotation on the map.
Use UIView animation to explicitly animate the user dot between user location updates. There is a tricky special case, which is that the callout must point to the annotation view’s implicit frame but must quickly rendezvous with the explicit frame.
Fixes#1041.
