/**
* SetUrl
* This is used to set up the other urls
* It is called statically so the Process method can use the url and have a way of setting the child object variables it needs to.
*
* @param String $url The url to use as the base for the others. It is trimmed of any trailing '/' characters so it'll be in a consistent format.
*
* @see _set_url
* @see template_url
* @see admin_url
* @see settings_url
* @see application_url
* @uses url
* @see Process
*
* @return Void Doesn't return anything. Sets a static class variable for easy access.
*
* @static
*/
public static function SetUrl($url = null)
{
self::$url = rtrim($url, '/');
}