Batch retrieval of elements by ID

I expanded the the driver.js functionality to retrieve a batch of elements.  getElementById then is just a 1 ID batch.  This makes it easy to iterate through elements by ID without incurring the overhead of a round-trip for each iteration.  My app's responsiveness improved a lot.

My fork has diverged even from upstream's master branch, but I think the affected content will be merged pretty easily.  Let me know if there's a problem and how I can help out.