Rename json-test to test_basic, since it has nothing to do with JSON anymore (at least not anymore than any other test does).

Rename ignore-test to test_ignore, too, for consistency with the names of test modules.

Do some chdirs in Python rather than in shell, because this commit otherwise causes mysterious "sh: 0: getcwd() failed: No such file or directory" errors to happen. This also solves an escaping bug quite nicely, though I still want to stop shelling out altogether eventually.