Refactor the web app bootstrapping code

- All custom JS variables are now preloaded into the `app.data` object, rather than directly on the `app` object. This means that admin settings are available in `app.data.settings` rather than `app.settings`, etc.
- Cleaner route handler generation
- Renamed ConfigureClientView to ConfigureWebApp, though the former still exists and is deprecated
- Partial fix for #881 (strips ?nojs=1 from URL if possible, so that refreshing will attempt to load JS version again)

src/Http/Controller/AbstractWebAppController.php

@@ -0,0 +1,52 @@
+<?php
+/*
+ * This file is part of Flarum.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Flarum\Http\Controller;
+
+use Flarum\Event\ConfigureWebApp;
+use Flarum\Http\WebApp\AbstractWebApp;
+use Illuminate\Contracts\Events\Dispatcher;
+use Psr\Http\Message\ServerRequestInterface as Request;
+
+abstract class AbstractWebAppController extends AbstractHtmlController
+{
+    /**
+     * @var AbstractWebApp
+     */
+    protected $webApp;
+
+    /**
+     * @var Dispatcher
+     */
+    protected $events;
+
+    /**
+     * {@inheritdoc}
+     */
+    public function render(Request $request)
+    {
+        $view = $this->getView($request);
+
+        $this->events->fire(
+            new ConfigureWebApp($this, $view, $request)
+        );
+
+        return $view->render($request);
+    }
+
+    /**
+     * @param Request $request
+     * @return \Flarum\Http\WebApp\WebAppView
+     */
+    protected function getView(Request $request)
+    {
+        return $this->webApp->getView();
+    }
+}