Added view strategies.

This allows a user to perform the following in a dispatchable action:

```php
$rows = array(
    array('Name', 'Email'),
    array('Ray', 'ray@example.com'),
    array('Joe', 'joe@example.com')
);

$model = new CsvModel(array(
    'content' => $rows
));
        
$model->setOption('delimiter', ',');
        
return $model;
```

The result is a file that is downloaded via the browser.