Add nucleus designation/attribution column to the later-stage output files

[vreuter]

Would be useful as a grouping unit to have the designation of which nucleus (i.e., cell) a record comes from be present in some later output files (e.g., the pairwise distances and the final traces). This could be accomplished with a join back to the original table with nucleus ID (on something like ROI ID), or by propagating the nucleus label through various steps, parsing it as part of each input record and emitting it back as part of each output record. Preference for the first since it makes each component more modular. NB: nucleus number is only unique per FOV, not globally across all fields of view for an entire experiment.