Add sets that a dev is assigned maintainer to the dev's "Sets" page

[suspect15]

A dev's "Sets" page currently displays sets for which they have authored at least 1 achievement or leaderboard. I think it would be interesting also add sets for which they are achievement maintainers. Perhaps changing the "Achievements" column to "Achievements authored" and adding a new column just after it "Achievements maintained" would be a viable option. The "Achievements maintained" column could similarly list "X" or "X of Y" depending if the dev is maintainer of some or all of a set's achievements.