USDZ format support

[bermannoah]

The new Apple x Pixar USDZ file format is going to be a thing, so we should try to parse it. Since it's a zip file of sorts maybe we can extend the existing zip parser to handle it. Will try to get my hands on an actual MIT licensed .usdz file -- for now though there's a spec sheet, and there are sample files here but there's no license file associated yet.