Get looptrace version number directly from data

[vreuter]

Once it's available, this project should pull the version number of looptrace which generated given data to read directly from the data itself, e.g. in metadata attribute(s) of a ZARR stack, or key-value of a JSON file.

Related to #4 , though in the sense of data provenance (this ticket) rather than in the sense of parameter / constant sharing (#4).