Added support for roles

Added the ability to use roles in ZfMvcAuth. The config syntax changed a
little. Now you have to specify the role name, which contain the old config syntax.

For example:

```php
'admin' => array(
    'Controller\Service\Name' => array(
        'actions' => array(
            'action' => array(
                'default' => boolean,
                'GET' => boolean,
                'POST' => boolean,
                // etc.
            ),
        ),
    ),
)
```