comments: add scores, rework comment menu.

* 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.

app/models/comment.rb

@@ -113,11 +113,6 @@ class Comment < ApplicationRecord
     end
   end
 
-  def voted_by?(user)
-    return false if user.is_anonymous?
-    user.id.in?(votes.map(&:user_id))
-  end
-
   def quoted_response
     DText.quote(body, creator.name)
   end