Remove the map's error view and it's associated resources.

Signed-off-by: Blake Skinner <bskinner@mit.edu>
Add a delegate method to report map view errors

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

Replace the use of the layer's anchor point and use the centerOffset property of MKAnnotationView instead. Also, there is no need to keep a retained copy of these images; let the system handle the caching.

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

More of the same, use centerOffset to position the image.

Signed-off-by: Blake Skinner <bskinner@mit.edu>
Make sure we also check all the base layers on a layer error. This chunk of code should probably be moved to a new method at some point.

Signed-off-by: Blake Skinner <bskinner@mit.edu>
Use MKAnnotationView's centerOffset property for positioning the annotations

Signed-off-by: Blake Skinner <bskinner@mit.edu>
Add methods for obtaining the matching MGSAnnotation for an MKAnnotation and retrieve/create views when needed.

Signed-off-by: Blake Skinner <bskinner@mit.edu>
Fix the annotation positioning again to incorporate the centerOffset. Any annotations should be using this to tweak the positioning of the annotation marker instead of using frame tweaks or CALayer's anchorPoint

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