Simplified and HTML lowered statement dumps

Initial import, adaptation, and cleanup of statement simplification, HTML dump. Original code by @zingales. This needs a review.
One small addition of my own which I wanted to point out: I added includes for `my.[css,js]`, and folded the default css and js into the html itself. The intention is:

- It's a trivial standalone thing with reasonable baseline behavior.
- It's very easy to customize the behavior by loading from a path with your own `my.*` extensions.