Add a /user_actions page. This page shows you a global timeline of
(almost) all activity on the site, including uploads, comments, votes,
edits, forum posts, and so on.
The main things it doesn't include are post edits, pool edits, and
favorites (posts and pools live in a separate database, and favorites
don't have the timestamps we need for ordering).
This page is useful for moderation purposes because it lets you see a
history of almost all of a user's activity on a single page.
Currently this page is mod-only. In the future it will be open to all
users, so you can view the history of your own site activity, or the
activity of others.
* Add comment scores.
* Rework voting buttons so that you can click the upvote/downvote
buttons to toggle votes.
* Hide the edit, delete, undelete, and report buttons behind a popup menu.
* Show the upvote/downvote/reply buttons to logged out users. Redirect
them to the login page instead.
Let users see when a post has deleted comments. Show normal users a
'[deleted]' placeholder when a comment is deleted. Show the full comment
to moderators.
Also fix it so that the comment creator can't edit or undelete deleted
comments, and users can't vote on or report deleted comments.
Finally, hide the creator_id, updater_id, and body of deleted comments
in the API.
