Licensing: Added licenses app view

Extracted many methods to a new "MetaController" in the process.

app/App/MetaController.php

@@ -0,0 +1,67 @@
+<?php
+
+namespace BookStack\App;
+
+use BookStack\Http\Controller;
+use BookStack\Uploads\FaviconHandler;
+
+class MetaController extends Controller
+{
+    /**
+     * Show the view for /robots.txt.
+     */
+    public function robots()
+    {
+        $sitePublic = setting('app-public', false);
+        $allowRobots = config('app.allow_robots');
+
+        if ($allowRobots === null) {
+            $allowRobots = $sitePublic;
+        }
+
+        return response()
+            ->view('misc.robots', ['allowRobots' => $allowRobots])
+            ->header('Content-Type', 'text/plain');
+    }
+
+    /**
+     * Show the route for 404 responses.
+     */
+    public function notFound()
+    {
+        return response()->view('errors.404', [], 404);
+    }
+
+    /**
+     * Serve the application favicon.
+     * Ensures a 'favicon.ico' file exists at the web root location (if writable) to be served
+     * directly by the webserver in the future.
+     */
+    public function favicon(FaviconHandler $favicons)
+    {
+        $exists = $favicons->restoreOriginalIfNotExists();
+        return response()->file($exists ? $favicons->getPath() : $favicons->getOriginalPath());
+    }
+
+    /**
+     * Serve a PWA application manifest.
+     */
+    public function pwaManifest(PwaManifestBuilder $manifestBuilder)
+    {
+        return response()->json($manifestBuilder->build());
+    }
+
+    /**
+     * Show license information for the application.
+     */
+    public function licenses()
+    {
+        $this->setPageTitle('Licenses');
+
+        return view('help.licenses', [
+            'license' => file_get_contents(base_path('LICENSE')),
+            'phpLibData' => file_get_contents(base_path('dev/licensing/php-library-licenses.txt')),
+            'jsLibData' => file_get_contents(base_path('dev/licensing/js-library-licenses.txt')),
+        ]);
+    }
+}