Have Path#closePath() handle merging of first and last segment, if doubled.

So we finally found a reason for #closePath() to stick around :)
Have Color always serialize in non-compact mode.
Export JSON with higher precision in tests, so comparisons of bounds do not fail.
Switch back to serializing segment lists for now, so we can fix other failing tests.
Fix issues with JSON symbol test code.

Export was working, but testing code was faulty.