add case status "resolved"

Since we now have a regulatory framework to tackle net neutrality violations and a few of them have already been positively resolved, we should also reflect that on RMN. Therefore I'd argue we need a new status for a case that marks it as "resolved". This can be set by the admins as it requires proper analysis of the situation. resolved cases could also be featured to send a positive message and encourage users to submit more potential violations.

There are already several cases in the system which should be in this status.