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/javascript/src/javascripts/utility.js

@@ -1,4 +1,5 @@
 import Rails from '@rails/ujs';
+import { hideAll } from 'tippy.js';
 
 let Utility = {};
 
@@ -70,6 +71,9 @@ Utility.dialog = function(title, html) {
   $dialog.find("form").on("submit.danbooru", function() {
     $dialog.dialog("close");
   });
+
+  // XXX hides the popup menu when the Report comment button is clicked.
+  hideAll({ duration: 0 });
 }
 
 Utility.keydown = function(keys, namespace, handler, selector = document) {