Large number of changes to CSS and table system

So we're using Nimbus heavily in PayPal Here and have relied heavily on CSS and table system from it. We've made a number of improvements to the CSS grammar (and the NITableViewSystem is new). This pull request is an "FYI" and basically a question of whether we should try to touch this up for merging back into Nimbus proper, or whether this fork is forever diverged...

Thoughts appreciated!