[TIMOB-9404] MobileWeb: Map - Add centerOffset property to Ti.Map.Annotation

See if Mobile Web can provide the same functionality. Original ticket: Add centerOffset property to a custom annotation to be able to set a x & y offset to the image of the annotation. Right now the center of the annotation is the center of the image size. This makes that some images appear not to be in their proper place at certain zoom levels. Reference to official documentation: http://developer.apple.com/library/ios/#documentation/MapKit/Reference/MKAnnotationView_Class/Reference/Reference.html#//apple_ref/doc/uid/TP40008207 I have already coded the feature and I open this ticket in order to get the pull request accepted.