Emphasize mutual follows on profiles, by default

I think on the website it would be nice if there was a display option (*enabled by default*) to merge people who would otherwise be in both the "Following" and "Followers" list into a new list "Mutual Follows", as mutual follows are generally more significant than one-sided follows.

As Mutual Follows would appear before "Following" and "Followers" lists (of course stripped of mutual follows), **this would have the side-effect of de-emphasizing one-sided follows, which would partially help with the problem of people getting followed by people they don't like**, as those would be pushed further down towards the bottom of the profile instead of being around the top if they are among the last people to have followed.

I still think an option to see the separate "Following" and "Followers" lists should be retained, as it can be interesting to see the chronological history of those, which the "Mutual Follows" option slightly obscures.

The issue names no files, tests, or entry points. Start by locating the website profile view and its Following and Followers list implementation, then determine how a default-enabled Mutual Follows option should affect ordering, filtering, and access to the original chronological lists.

Written by the indexing model from the issue text.