Polish AnnotationUtils

- Added explicit reference to “get” and “find” lookup types in the
  class-level Javadoc.
- Updated documentation for the underlying algorithms in
  findAnnotation(Method,Class) and findAnnotation(Class,Class) in line
  with the status quo.
- Reverted recent changes to findAnnotationDeclaringClass() by removing
  meta-annotation support in order to maintain backwards compatibility
  with previous releases.