Fixed Inheritiance bug and Circular Reference Exception

* When using multiple `extends` in PHP, the order was wrong
* The circular reference path was incorrect when mixing PHP's `extend` and mapping extends, made the exception message less verbose.

Fixes https://github.com/symfony-cmf/RoutingAutoBundle/issues/90
The message is in very readable English text, we just don't have to verify that in the test imo. We have to test that it is a circular reference for the expected class imo