Demo site removed

Remove the demo site from the site folder but keep the site folder in
the trunk.
Gitignore

Ignore all files in the site folder except the gitkeep file.
Override standard pages

Standard pages can now be overridden by the user by simply creating a
page with the same name as the standard page to overload. Eg: create a
"404.php" page in the website-side "standard" folder to override the
default 404 page. The "standard.css" file is dedicated to overload
standard styles of your pages.