Convert english translation file

- convert english translation to translate key
- remove baggy template for login (never used since user isn't logged in and it'll use the default theme: material)
- fix tests about text in response (now checking translation key instead of translated text)
- remove all ugly `<div class="hidden">{{ form_rest(form) }}</div>`

src/Wallabag/ImportBundle/Tests/Import/WallabagV2ImportTest.php

@@ -45,7 +45,7 @@ class WallabagV2ImportTest extends \PHPUnit_Framework_TestCase
 
         $this->assertEquals('wallabag v2', $wallabagV2Import->getName());
         $this->assertNotEmpty($wallabagV2Import->getUrl());
-        $this->assertContains('This importer will import all your wallabag v2 articles.', $wallabagV2Import->getDescription());
+        $this->assertEquals('import.wallabag_v2.description', $wallabagV2Import->getDescription());
     }
 
     public function testImport()