[TIMOB-7697] Ti API: Improve Animation APIs

In the layout API proposal, we explicitly mention property batching; we need to revisit the animation API to figure out a good way to allow batching, to ensure that the system performs animations a_1 and a_2 concurrently if the user requests. This might look like:

var a_1 = Ti.UI.createAnimation({view:v1, ...});
var a_2 = Ti.UI.createAnimation({view:v2, ...});

Ti.UI.animate(a_1, a_2);

This API improvement is a direct result of filing TIMOB-7693 and repeated reports from QE about the animations in TableView Layout 3 not being in sync.