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.

Also we can apply highlighting later on `Events` debug panel if it will be considered as enh. , there we can highlight json encoded event attributes and data .

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/1748844/3269348/c43f2a40-f2eb-11e3-8f39-c407c41c7e35.png)
![log_panel_highlight](https://cloud.githubusercontent.com/assets/1748844/3269350/ca12029e-f2eb-11e3-84e0-29e7eb8db2d8.png)
![profile_panel_highlight](https://cloud.githubusercontent.com/assets/1748844/3269351/ce932e6a-f2eb-11e3-9111-3d1b6d568d01.png)