fix cluster numbering in the absense of Hilbert_Choice (reverts acde1b606b0e, effectively reintroducing most of 0bfaaa81fc62)
By chapter:
chapters 1 and 2, maybe 3: Peter White
chapters 6, 7 and 8: David von Oheim
chapter 6, maybe 8: Gerwin Klein
chapters 3, maybe 4: Tanja Vos
chapters 1-3 at least: Stefano Bistarelli