release/21.6.22

Ewelina Maria Lobodzinska

@ewelina

ee1c8634 · Merge branch '21.6-io' into '21.6' · Mar 07, 2020

PowhegOTF-00-04-03
ReadHepMCFromFile added to TruthIO
MGControl improvements
Update filters to GeneratorFilters-00-03-71 tag
fixes to Pythia8_i