Add badge for banned users profiles

[suddenwhipvapor]

Following on #3181 it would also be very useful to immediately see if a profile was banned by attaching a small badge (similar concept for mediators/moderators badges) to his profile icon.

[HenrikJannsen]

Not sure if we want to give banned users the info, so they create a new account and keep doing their malicious activity which led to a ban. We should only ban users in severe cases. I know that recently with the scammers and the many suspicious offers there have been false positives, but I think that was an exceptional situation and hopefully we don't get that again.