Updates to title, abstract, intro

I made lots of changes to the abstract, largely to spend more time motivating the problem, focus the reader's attention on the contributions, and be more specific about the evaluation results.

Take a look at the diff so you can see exactly the changes I made. The goal would be that even though I made them, you can pick up the tricks I used and apply them yourself in future papers.

I tried an alternate title. See if you like it? I'm not strongly attached, vs. the prior one, but I think it sounds slightly more general than the term "formal".

I'll move to the design section next.