Initial version of libgames-scores

Fake pull request for initial review of libgames-scores.

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I'd rather not use a default parameter for the style. This is kind of magic; games should be required to specify it.  Default parameters make sense only when there's a particular option that makes sense most of the time (usually 0 or null), but here all the options are equally plausible and it would harm readability for games to omit.