Code base for 1.8

- Fix all php errors (at least the ones I found)
- Rewrite root index based on Coding Style
- Add new medias inclusions system (Allows to include css and js files from modules and template
- Add new design of global notifications (private message, install dir, site closed)
- Delete popup notification for private messages
- Include jQuery (embedded version 1.8.3) by default only if it is not already included by the template