Move config/permission actions to API; clean up cache flushing

src/Support/ClientAction.php

@@ -118,6 +118,17 @@ abstract class ClientAction extends HtmlAction
         return $view;
     }
 
+    /**
+     * Flush the client's assets so that they will be regenerated from scratch
+     * on the next render.
+     *
+     * @return void
+     */
+    public function flushAssets()
+    {
+        $this->getAssets()->flush();
+    }
+
     /**
      * Set up the asset manager, preloaded with a JavaScript compiler and a LESS
      * compiler. Automatically add the files necessary to boot a Flarum client,