AutoTimestamp annotation support for non persistent super classes

[codeconsole]

Previously annotations would only be detected if the super class was another domain class.

This allows a domain class to have parent class that is not a domain class and still utilized the @AutoTimestamp annotation

e.g. this now works and does not work without this fix
src/main/groovy/example/Media.groovy

class Media {
     @AutoTimestamp Date modified
}

grails-app/domain/example/Image.groovy

class Image extends Media {
     String format
}

grails-app/domain/example/Video.groovy

class Media extends Media {
      int frames
}

[sbglasius]

Good addition, but I would like to see an accompanying test to prove the correctness of the changed code