Added 3DSECURE

This should fix issue https://github.com/rezzza/PaymentBe2billBundle/issues/16.

The default display mode for 3DS can be configured in the bundle (defaults to `main`):

```yaml
rezzza_payment_be2bill:
    default_3ds_display_mode: main / top / popup
```

To use 3DSecure, extra data parameters can be added to the payment https://github.com/rezzza/payment.vlr/blob/master/src/Vlr/ChargeBundle/Backend/Be2bill.php#L99.

- `3DSECURE` = `yes` (required to enable 3DS)
- `3DSECUREDISPLAYMODE` = `main` / `top` / `popup` (optional, will default to the Bundle configuration)

When the deposit is made, if the transaction is secure, it will throw a `SecureActionRequiredException` that will be caught by the Plugin controller https://github.com/schmittjoh/JMSPaymentCoreBundle/blob/master/PluginController/PluginController.php#L403-L420. The transaction will be pending until the callback is received.

The html needed to display the form can then be accessed with:
```php
$html = $result->getPluginException()->getHtml();
```
Good idea to replace strings by consts :+1: