Prearchive notification emails

Users are sometimes forgetting to finish archiving data that's uploaded via the uploader applet. It ends up sitting in the prearchive and no one knows about it.

So we need a feature that sends an email notification to the uploader + a list of additional subscribers when a session has been in the prearchive longer than xx minutes. The service should be optional and configurable on a per project basis.

It should send an initial email after xxx minutes and follow up emails every yyy minutes.

NOTE: Maybe this should all wait until we've refactored the prearchive implementation to use Hibernate instead of the current roll-your-own code base.