FR - Make CCA dismissable

[JiveDig]

This will be needed when we have pop-ups and slide-ups, but it would be cool for site notices (before header) as well. If someone closes it, it will set a cookie so we know not to show it for that person again.

We'd need some minimal settings for how long to hide it for.

Also how would we add the "dismiss" or "close" link? For pop-ups it's easy. But for other stuff we have no idea what the content will look like in there.

It could be a button with a custom class or something, but it gets complex.