Teach MetaHelper::meta() to accept array from 'Meta' configure key

Allows:

```php
	Configure::write('Meta', array(
		'author' => 'rchavik',
		array('attribute' => 'og:author', 'content' => 'rchavik'),
		array('http-equiv' => 'refresh', 'content' => '5'),
	));
```

To generate:
```html
	<meta name="author" content="rchavik">
	<meta attribute="og:author" content="rchavik">
	<meta http-equiv="refresh" content="5">
```