Add concept of "unresolved" or "unanswered" posts

[ewinslow]

Goals:

• Posts needing answers don't get lost.
• Posts that don't get answers are truly bad/unclear posts, not just lost in the void.
• Improve time-to-resolution for community-asked questions.

As is, posts with the most activity wind up at the top, which is good for discussion, but unpopular posts that need answers can slip off the end of the page quickly without anyone noticing. That's pretty discouraging for people who are looking for support.

Here are the basic features I envision:

• New forum posts are marked as "Needs resolution" by default. If the post is only for discussion purposes, you can uncheck the box.
• Existing posts are not marked as "Needs resolution"
• There is a new "unresolved posts" tab under "discussions" that lists posts still needing resolution oldest first.
• Site admins, group admins, and original posters can mark "Needs resolution" posts as "resolved" at their discretion. This closes comments for that post, and takes it off the "unresoved posts" page.
• Can mark a "Needs resolution" post as not needing resolution without closing it and vice-versa (correct mistakes).

More advanced features:

• Maybe auto-resolve posts after an arbitrary time limit if there's no activity?
• Statistics: number of resolved/unresolved posts over time, time-to-resolution, etc.
• Email reminders -- "Did these answers resolve your issue?"

Problem: I suspect people don't generally want to take explicit action to mark their post as resolved. Could end up requiring a lot of manual curation by the admins (urgg...). How to streamline this? Email reminders could help. Auto-resolving could help (e.g. Stack overflow auto-selects one of the answers after a certain period).

[ewinslow]

A simpler version of this could just be tracking posts that haven't gotten responses. That could even be really good for discouraging bumps since bumping would remove it from the "unreplied" list.

Just need to cache the total replies count on the topic entity. Filter for the ones with a zero value. Hmm... Another use case for a computed values API...