Rename existing mailing list stuff

Since we're not really giving people the ability to "opt in" on this, it
seemed confusing to leave the code structured like that. Now we can just
check if they have not opted out to determine if we can send mail.
Add ability to send mailing list type messages
Add unsubscribe link
Add message about unsubscribing
Commit for testing mailing list
Merge branch 'mailing-list' into staging2