Added support for CusttomAnnotationView class

[kostassite]

Added a method in VPPMapCustomAnnotation protocol so I can use an extremely custom annotationView when not in clusterMode. To use it just need the Annotation to implement this method and return the CustomAnnotationView.

[enchhuang]

when I use this example, I can't compile success, because #import "MapAnnotation.h" not found in project. Can you fix this problem? Thanks.