abstain.tif now tells unmeasured vertices apart: 1 kept its published position, 2 moved by the offset filled in from measured neighbours. Coordinates and the other grids are unchanged; meta.json notes, release.json, index.json, the card, load_example.py and SHA256SUMS are updated.
Snapped surface labels v1: 108 segments of PHerc0139, PHerc0814, PHerc0841 and PHerc0172 (part 2)
