added highlighting into debug module

Added basic highlighting in `Debug` module with [this](https://github.com/scrivo/highlight.php) 3rd party lib. By default css similar to `github`. Since we dont have too particular code to highlight in `Debug` module, i've currently only highlighted sql queries + categories strings. Questions to discuss:

- should we highlight other pages with this one? Or we can skip it and make it later with simple css if needed and not wrapping them into `<pre>` highlight element like it is done for `category` attribute for example.

Any suggestions on how to highlight better would be very welcome ) Below are screenshots of highlighted pages:

![database_panel_highlight](https://cloud.githubusercontent.com/assets/1748844/3269330/7704c276-f2eb-11e3-92c0-33e494961c80.png)
![log_panel_highlight](https://cloud.githubusercontent.com/assets/1748844/3269332/7c19002e-f2eb-11e3-997d-b79a14ada41e.png)
![profile_panel_highlight](https://cloud.githubusercontent.com/assets/1748844/3269333/7ffcd3fa-f2eb-11e3-8cfa-bd0cb19242f0.png)