Massive JavaScript cleanup

- Use JSX for templates
- Docblock/comment everything
- Mostly passes ESLint (still some work to do)
- Lots of renaming, refactoring, etc.

CSS hasn't been updated yet.

framework/core/src/Locale/JsCompiler.php

@@ -13,12 +13,15 @@ class JsCompiler extends RevisionCompiler
 
     public function compile()
     {
-        $output = "var app = require('flarum/app')['default']; app.translator.translations = ".json_encode($this->translations).";";
+        $output = "var initLocale = function(app) {
+            app.translator.translations = ".json_encode($this->translations).";";
 
         foreach ($this->files as $filename) {
             $output .= file_get_contents($filename);
         }
 
+        $output .= "};";
+
         return $output;
     }
 }