EZP-22152: list used templates in the web debug toolbar

http://jira.ez.no/browse/EZP-22152.
Re-launch of https://github.com/ezsystems/ezpublish-kernel/pull/382 by @dspe.
Matching ezpublish-community pull-request: https://github.com/ezsystems/ezpublish-community/pull/96.

### What
Adds the list of twig and legacy templates that were used to render the response to the Symfony 2 profiler.

### How
- introduces `EzPublishDebugBundle`. Currently contains the SPI & templates logging toolbar elements
- extends the existing toolbar code to add templates
- reads legacy templates list using a legacy callback
- wraps Twig display() in a call that measures execution time and register the call using `eZ\Bundle\EzPublishDebugBundle\Collector\TemplateDebugInfo`

### TODO
- [ ] Add tests when applicable
- [x] Add the HTML comments debugging feature around twig templates (*Q: does this require an option ?*)

### Screenshots

**Debug Toolbar**
![ez debug toolbar](https://f.cloud.github.com/assets/235928/1997015/813e95a0-851d-11e3-98e6-5bdae3cb7d0e.png)

**Profiler page**
![capture decran 2013-05-30 a 15 27 25](https://f.cloud.github.com/assets/329691/585011/f15c39a8-c92c-11e2-99ed-a894388fe6c9.png)

**Legacy Templates**
![capture decran 2013-05-31 a 10 55 18](https://f.cloud.github.com/assets/329691/589888/d959da60-c9cf-11e2-95f6-e527dde6db97.png)