Make sure we don't pop any callouts for things that don't want or need them.

Signed-off-by: Blake Skinner <bskinner@mit.edu>
Implement the stayCenteredOnUserLocation property

Signed-off-by: Blake Skinner <bskinner@mit.edu>
Make sure we don't already have the annotation selected

Signed-off-by: Blake Skinner <bskinner@mit.edu>
Dead code elimination

Signed-off-by: Blake Skinner <bskinner@mit.edu>
Make sure we animate the region change prior to displaying a callout

Signed-off-by: Blake Skinner <bskinner@mit.edu>