Use Drupal's AJAX framework

Rules links has its own implementation of the AJAX call and response process. This patch converts rules links to drupal's native AJAX system.

A few notes:

• This adds ctools as a dependency...but its a views dependency so its basically on every site anyway
• This increases the accessibility of the module. If the user doesn't have JS, the link reverts to the behavior of a normal non-ajax link
• This also opens the door for adding configurable actions to happen after the link is clicked, rather than just displaying a message. I could imagine setting jQuery selectors in the rules admin UI, and adding / removing additional content after the rules link calls back. I'd be interested in working on that functionality should this patch be accepted