Consider notification feature for PPVers when projects drop into PPV Available

[windymilla]

Quite possibly not worth the effort/complication, but...

1. Some PPVers might find it helpful (and be prompted to pick up a project) if they were notified when any project transitions to PPV Available (i.e. not just an event notification that they subscribe to for each project).
2. It would need to be optional, probably default to "on", but a PPVer could opt out.

Or some similar way for PPVers to be alerted whenever any project becomes available for PPV