More work on the choice prototype. It's broken now, but it's ready to be
reincarnated as the main code.

-Peter Mawhorter
Got the prototype working again and pushing all the way through to
ChoiceScript. A future commit will deal with the chaos in rules/story.

-Peter Mawhorter
Revamped the story rules based on the choice prototype. Next step is to
hack up a task framework in Python that works with the new rules.

-Peter Mawhorter
Untangled some pretty nasty bugs, including some that I think are
related to clingo bugs.

-Peter Mawhorter