Get tinyjs running (v1); pull out {dbg,run}.py.

This is another milestone.

I'm sure there are plenty of bugs in the current tinyjs grammar in sample12.
But first I want to get previous tests working, and make sure I still see what
I expect from sample[7-11]. I have a bunch of code debt, so I might address
that soon, including disallowing parse.py to be main, and pulling out tests to
their own module.