Send admins notifications about appeals

[dqwiki]

In continuance of: #619 Shared overlap: #438

Tasks:

• [x] Allow the storing of reviewer emails
• [x] Verify stored emails using methods from #438
• [x] DO NOT USE THE ONWIKI EMAIL SYSTEM FOR THIS - this is opt-in, not opt-out
• [x] Set preferences on when user would like an email, and how frequently: On action (user replies/return to main queue while assigned), weekly (appeals of your blocks)
• [ ] Send email per above
• [x] Log privately that the email has been sent and the type/details