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/Handler/ControllerRouteHandler.php

@@ -0,0 +1,71 @@
+<?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\Handler;
+
+use Flarum\Http\Controller\ControllerInterface;
+use Illuminate\Contracts\Container\Container;
+use InvalidArgumentException;
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+
+class ControllerRouteHandler
+{
+    /**
+     * @var Container
+     */
+    protected $container;
+
+    /**
+     * @var string
+     */
+    protected $controller;
+
+    /**
+     * @param Container $container
+     * @param string $controller
+     */
+    public function __construct(Container $container, $controller)
+    {
+        $this->container = $container;
+        $this->controller = $controller;
+    }
+
+    /**
+     * @param ServerRequestInterface $request
+     * @param array $routeParams
+     * @return ResponseInterface
+     */
+    public function __invoke(ServerRequestInterface $request, array $routeParams)
+    {
+        $controller = $this->resolveController($this->controller);
+
+        $request = $request->withQueryParams(array_merge($request->getQueryParams(), $routeParams));
+
+        return $controller->handle($request);
+    }
+
+    /**
+     * @param string $class
+     * @return ControllerInterface
+     */
+    protected function resolveController($class)
+    {
+        $controller = $this->container->make($class);
+
+        if (! ($controller instanceof ControllerInterface)) {
+            throw new InvalidArgumentException(
+                'Controller must be an instance of '.ControllerInterface::class
+            );
+        }
+
+        return $controller;
+    }
+}

src/Http/Handler/RouteHandlerFactory.php

@@ -0,0 +1,38 @@
+<?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\Handler;
+
+use Illuminate\Contracts\Container\Container;
+
+class RouteHandlerFactory
+{
+    /**
+     * @var Container
+     */
+    protected $container;
+
+    /**
+     * @param Container $container
+     */
+    public function __construct(Container $container)
+    {
+        $this->container = $container;
+    }
+
+    /**
+     * @param string $controller
+     * @return ControllerRouteHandler
+     */
+    public function toController($controller)
+    {
+        return new ControllerRouteHandler($this->container, $controller);
+    }
+}