Bug: hard coded url

In advertising-manager.php:

define('ADVMAN_URL', get_bloginfo('wpurl') . '/wp-content/plugins/advertising-manager');

Should be changed to something like:

define('ADVMAN_URL', plugins_url('',__FILE__));

This would help prevent breakage when people move the default directories around.

https://ww.wp.xz.cn/plugins/advertising-manager/