Support servers not using url rewriting

This is a small mod which allows fatfree to run on servers not supporting url rewriting. By supporting URL in the following format http://localhost/folder/index.php/worker/main

The variable  `$_SERVER['REQUEST_URI']` is translated from `/folder/index.php/worker/main` to `/worker/main`.

This new feature can be enabled by setting the setting `REWRITE` to FALSE