Add support for ordering an object's collections at the SQL / DB level

This would be quite useful in some cases, as currently default sorting can only be done via Java (using a SortedSet and implementing comparable on the collection's entities).

Hibernate supports this via the OrderBy annotation, so the only work is to create the glue between Grails and Hibernate (this would probably be part of the GORM DSL I guess). I can provide an example Hibernate mapping file for this if needed, or the following links show how to achieve that:

http://www.hibernate.org/hib_docs/v3/reference/en/html/collections.html#collections-mapping (XML mapping)

http://www.hibernate.org/hib_docs/annotations/reference/en/html_single/#entity-mapping-association-collections (Annotations)