[Observium] Alerting association changes

Hi Guys,

I've just committed some changes to extend the new rule parsing to alerting. At the moment we're just testing it, so it doesn't do an automatic migration (and there's no editing interface yet!)

If you're using alerting (and are running the current version, not stable or CE), you can go to /migrate_alerts/ on your Observium installation to see if the rules will work properly when we make the change for real. Nothing will be changed at this point, we just generate the new rules and make sure their outcome matches what's in the database.

If you get any errors, send me a screenshot of the page with the queries visible so we can fix it!

Oh, and make sure you do an alerting rebuild first!

Thanks, adam.