Refactor Annotations (#721)

- Old Annotation renamed to deprecated LegacyAnnotation
- Annotation is now a trait that can be extended
- New JsonProtocol for Annotation [de]serialization
- Replace AnnotationMap with AnnotationSeq
- Deprecate Transform.getMyAnnotations
- Update Transforms
- Turn on deprecation warnings
- Remove deprecated Driver.compile
- Make AnnotationTests abstract with Legacy and Json subclasses
- Add functionality to convert LegacyAnnotations of built-in annos
This will give a noisy warning and is more of a best effort than a
robust solution.

Fixes #475 Closes #609