[TIMOB-8970] MobileWeb: Rearchitect animation system

The current animation system relies on CSS3 transitions. This is great for all devices except IE9 and Windows Phone 7.5. To support those platforms, we need to add a code path for old school setTimeout() animation. One possible solution is to scrap CSS3 transitions completely and use requestAnimationFrame with a setInterval() fallback. This would offer greater compatibility and flexibility over transitions. Here's some articles that might be of interest: * http://paulirish.com/2011/requestanimationframe-for-smart-animating/ * http://creativejs.com/resources/requestanimationframe * https://gist.github.com/1002116