Fix alert counts

[sbulen]

Three changes:

• Addressed an issue where alert counter was not getting updated for all subscribers on replies. This is a bug that definitely impacts the alert counter and popup.
• Used the standard calculation in one instance where the logic looked a little sketchy.
• Removed an erroneous calc, where it was updating the alert counter with new unread, instead of all unread. Not sure it was necessary there anyway.

[sbulen]

I've been running this on my site the last couple of days. Alerts are delivered much more consistently now.

Also, I periodically audit the alert counter, and it is now perfectly aligned with the alerts, and does not fall out of sync anymore.