Add afterWork flag for ChangeTriggers which allows a change trigger to run in its own transaction.

By default, trigger classes executed after a request has been processed will be running in the same transaction as the main code. This may cause problems for code that wants to delete objects / object graphs which have not been persisted properly yet. The afterWork flag will run the post-code of the trigger in its own transaction after the request's database changes have been committed.
Fix problems when removing custom metadata.

MetasetService.unlinkMetaset was not working properly, in some cases it would throw an exception because the selected metaset could not be deleted.