Add :autofollower_nicknames to let any users autofollow all new users

This is the exact same thing as :autofollow_nicknames, except the reverse. Rather than new users following some particular user(s), a list of particular users will follow all new users.

This creates more of a "Tom from MySpace" vibe than "Mark from Facebook." Being followed gives users a sense of validation, and it can help them feel like they're supported by the instance admin.

A user can be added to both :autofollow_nicknames and :autofollower_nicknames to make them mutuals. Personally I think autofollowing causes confusion, and it's a better first-time experience to see an empty timeline with instructions: "Welcome to your home feed, you must follow someone to see something here," so having a user follow them instead is a better solution.