Chance of rendering several tags og: image in pages

'renderOGMetaTags' function needs to be able to be an array, eg - when registering several images need to have the usability of thumbnails on facebook.

```
public function renderOGMetaTags() {
    $this->ogTags['fb:app_id'] = $this->appId; // set this app ID og tag, for Facebook insights and administration
    if (!isset($this->ogTags['og:type']))
      $this->ogTags['og:type'] = 'website'; // set website as the default type
    if (!isset($this->ogTags['og:title']))
      $this->ogTags['og:title'] = Yii::app()->name; // default to App name
    if (!isset($this->ogTags['og:url']))
      $this->ogTags['og:url'] = $this->getProtocol()."://".Yii::app()->request->serverName.Yii::app()->request->requestUri; // defaults to current URL
    foreach ($this->ogTags as $type => $value) { // loop through any other OG tags declared
        if(is_array($value))
        {
            foreach ($value as $v)
                $this->registerOpenGraph($type, $v);
            continue;
        }
      $this->registerOpenGraph($type, $value);
    }
  }
```