Add State of Mozilla 2012 page. Bug 928120.

- Update video helper to accept 'preload' & 'id' attributes.

- Add image replacement class to sandstone/lib.less.

- Add default title style to mozilla-modal.js.
Merge pull request #1420 from jpetto/bug-928120-state-of-mozilla-2012

Add State of Mozilla 2012 page. Bug 928120.