#916 Broadcast emails

[macalter]

In keeping with best practices of sending "bulk" emails, it would be helpful (I think) to have a set "opt-out" phrasing that can tag onto outgoing emails.

I understand PGV cannot handle automated opt-out process itself but the phrase to the effect "you are receiving this.... if you no longer wish to...." contact "xxx". would be good.

I want to use broadcast emails to let people know about updates. But, just because they're registered it doesn't mean they want to receive them regardless of frequency.