Replace is_personal_server flag

[brassy-endomorph]

fixes #646 fixes #626

• Removes IS_PERSONAL_SERVER flag and is_personal_server jinja var
• Removes hardcoded riseup.net text and replaces with SMTP_FORWARDING_MESSAGE_HTML env var
• Changes logic for /directory route to use DIRECTORY_VERIFIED_TAB_ENABLED env var instead of IS_PERSONAL_SERVER
• Removes ProxyFix that has dubiously correct settings with unused results
• Detects "personal server / Tor" via request.host
• renamed JS files (didn't change them, but the diff thinks I did)
• adds docs for all currently supported configs (others exist, but they're purposely undocumented so we don't have to support them)