Add logger and stopwatch for Doctrine queries

Add SQL queries to the logs using the DbalLogger of the DoctrineBridge.

In addition, if the WebprofilerServiceProvider is registered (stopwatch service set), the timeline show doctrine queries.

![Profiler](https://f.cloud.github.com/assets/400034/152414/877dc396-75c4-11e2-96df-6dde93c7d86e.png)