Discussion posts should update "last updated by" and "last udpated on" fields

We would like the Last Update On and Last Updated By fields to be impacted by discussions and not just changes to the field data.

We often look at cases to see if there has been any recent activity. The last updated fields are a good way to tell this, but they don't get updated if someone posts a new discussion.

As it is now, it can look like a case or a task has had no activity, but in reality an active discussion can be occurring, but you can't tell that unless you drill into the object.