Enable PHPStan

- Fix error for level 0 & 1 (level 7 has 699 errors...)
- Add `updated_at` to site_credential (so the `timestamps()` method applies correctly)

tests/Wallabag/CoreBundle/Helper/RedirectTest.php

@@ -17,6 +17,9 @@ class RedirectTest extends TestCase
     /** @var Redirect */
     private $redirect;
 
+    /** @var UsernamePasswordToken */
+    private $token;
+
     public function setUp()
     {
         $this->routerMock = $this->getMockBuilder('Symfony\Component\Routing\Router')