Add cookies notification bar.

This adds a small, not too intrusive, bar at the bottom of the page. The message would probably need to be improved.

Hiding of the bar is handled in 2 ways. For those who have JS enabled it's hidden using JS and a cookie is set (for duration 1 day) to prevent displaying the bar again. If JS is disabled in the browser there would be a form submission and a flag is set in the session to prevent displaying the bar again.