creationTime header is coarser than the other timestamps in the same document #617

Header/@creationTime is written with getCurrentTime(GMT), so it floors to a whole second:

deviceModelChangeTime, in the same Header element twenty lines later, uses GMT_UV_SEC:

Asset timestamps and observations use it as well, which makes creationTime the coarsest timestamp in the document. I couldn't find a config option that reaches it.

Same in the JSON printer: json_printer.cpp#L67

It matters for clients using creationTime as a remote clock reading, where whole-second resolution caps the measurement at ±0.5 s.

Switching both call sites to GMT_UV_SEC needs no schema change.