Optional defineOnFirstUse for MVA, rng_max* fix, printout helper
As was already done for scalefactors in https://gitlab.cern.ch/cp3-cms/bamboo/-/merge_requests/124; it should solve the potential segmentation fault in
mva = op.mvaEvaluator(...)
result = op.switch(<inputs-are-valid>, mva(<inputs>, defineOnFirstUse=False), <default-value>)
CC @gsaha
Edited by Pieter David