Quick and dirty patch to allow _latest and _latestPost URLs for Web Profiler

Allows you to use URLs like http://acmeproject/app_dev.php/_profiler/_latestPost?panel=swiftmailer and just reload it each time you're testing a page which handles a POST then bounces elsewhere (or renders some GET sub-requests after the POST).

You can also use _latest to just view the most recent request's debug info.