Make a hobbits python package

Now that there's some proof-of-concept stuff for embedded python from #23 , it should just be a matter of some build engineering and some API refactoring and expansion to make a hobbits python package. At first, this will mostly be useful for making tools like the runner, the tester, and the web server ( #47 ).

Start by reviewing the embedded-Python proof of concept in #23 and the runner, tester, and web-server work referenced by #47. Define the package boundary, API changes, and build requirements before implementation; done means those tools can use the resulting Python package.

Written by the indexing model from the issue text.