Pull in gallerycss-csslist into core

Hey @msweeney, I'd appreciate it if you could take a look at the CSS here in CSSList. I pulled out a bunch of styles for `.yui3-menu-dark`, and `.yui3-menu-light` since we can do that with the skinner. The styles in here are for a generic horizontal and vertical list, a fixed list, and a paginator. 

Let me know what you think. These styles are largely inspired by Ryan's work on `gallery-sm-menu`. 

Take a look at 6677c3f for the details.