Emoji: Eliminate unused images, make sure panel clicks add emoji (#1849)

* Emoji: Ensure that all clicks work by using emoji data directly

* Eliminate a number of unused emoji images from final build

* Re-add the generic sheets directory, which we partially filter

preload.js

@@ -53,6 +53,7 @@
   }, 1000);
 
   window.EmojiConvertor = require('emoji-js');
+  window.emojiData = require('emoji-datasource');
   window.nodeFetch = require('node-fetch');
   window.httpsAgent = require('https').Agent;
   window.nodeBuffer = Buffer;