[WIP] Plug new authentication front app to backend app

- [x] Add IE 7 compatibility
- [x] Add controllers tests

**To get the new front working**

- run ```bower install``` in the root directory (to fetch asset dependencies)
- run ```npm install``` in www/assets/bootstrap directory (this will fetch required dependencie to build less files)
- run ```bin/setup l:c``` in root directory (to build less files)

**Things to know**

- Each login template rendered by twig use a custom form layout template to display form from symfony/form component so be sure to override the defaut form template in login controller

```php
$app->before(function() use ($app) {
    $app['twig.form.templates'] = array('login/common/form_div_layout.html.twig');
});
```

- Angular JS form validation binding relies on the form name so be sure to create a named form with symfony/form component that match the name used in the controllers and defined in www/skins/login/js/angular/app/app.js file

Sample :
```php
$form = $app['form.factory']->createNamedBuilder('loginForm', 'form')
                ->add('email', 'email', array(
                    'label' => _('E-mail'),
                    'required' => true,
                    'disabled' => $app['phraseanet.registry']->get('GV_maintenance'),
                    'constraints' => array(
                        new Assert\NotBlank(),
                        new Assert\Email(),
                    ),
                ))
                ->add('password', 'password', array(
                    'label' => _('Password'),
                    'required' => true,
                    'disabled' => $app['phraseanet.registry']->get('GV_maintenance'),
                    'constraints' => array(
                        new Assert\NotBlank(),
                    ),
                ))
                ->getForm();
```