Idea: Moderation tools

Twice now I've found that someone had opened up one of my "quick-fix" challenges and hit "yes" a few hundred times without reading the instructions. I know it's partly my fault for making a challenge so easy to mess up, but it would still be nice to have better ways to repair or prevent the damage. For example:

• Allow an admin to mark tasks for review, even if the user didn't request it (see also #1068)
• Include the quick-fix changeset in the export CSV
• Button to revert the quick-fix changeset from task review
• Go to a user's profile from Task History, and to their OSM profile from their MR profile
• Filter task list by user or completion time just noticed I can do this with "configure columns"
• Require a minimum editing time
• Revoke points or otherwise penalize bad edits
• Ban users from participating in a challenge (have not needed this yet)

Related issues: #791, #454

Start by reading related issues #1068, #791, and #454, then inspect the existing task review, export, and history flows. The issue lists several possible moderation capabilities rather than naming one scope; work would need a selected capability, defined acceptance criteria, and verification that the corresponding user flow is complete.