Initial drop of CSSForm from the YUI 3 Gallery.

About
--------

This commit pulls in [CSSForm](https://github.com/tilomitra/cssforms/) from the YUI3 Gallery as of gallery-2013.03.27-22-06. The CSSForm repo can be found [here](https://github.com/tilomitra/cssforms/) with more granular commits.

This pull request introduces some small changes to CSSForm, mostly with the `meta/` and `build` file changes. The docs are empty right now, because they will probably live on YUI CSS. 

The CSS is up-to-date as of [f9c1d64d](https://github.com/tilomitra/cssforms/commit/f9c1d64da6794765f5929c06ee0b78bb84260a3c) which is CSSForm v0.2.1.

To get a sense of the CSS in this pull request, you should go to the [demo page](http://tilomitra.github.com/cssforms/).

Reasons for pulling it into core
-------------------------------------------

Forms, especially laying out forms, are a nuisance on the web. There are certain common styles which are used time-after-time and I think it makes sense to group them in one place such as this module. In addition, laying out forms comes with a fair share of cross-browser-compat issues. Luckily, Normalize takes care of these. CSSForms wraps up these rules (in `forms-core`) and makes it easy for people to create forms by adding class names. Since CSSNormalize is part of core, it makes sense for low level building blocks such as menus, forms and tables to be part of core too.

While working on YUI CSS, I tested this on IE7+, Latest FF, Chrome & Safari, iOS6. 

//cc @msweeney @jconniff @ericf