prettify code tags

I know 1.0 is feature frozen but well.. :D 

Not sure if this should be part of the Elk Core  or better be an addon.. It integrates google code prettify.. the screenshot is self-explaining.. Haven't added an UI part for the enableCodePrettify var yet, if you wan't to test yourself you need to add enableCodePrettify = 1 in elkarte_settings.


![prettify_code](https://f.cloud.github.com/assets/1027992/1805705/9b2ecb68-6c8d-11e3-96b8-3fc546b14234.png)