Fix ASCII HepMC reader/writer to scale units correctly
Port merge of branch 'fix_ascii_unit_conversion_sim09' into 'Sim09-upgrade'
See merge request !456 (merged) into 'Sim09'
(cherry picked from commit 4e26c561)
fa683424 Removed GeneratorUtils::scale method and replaced by native HepMC
628fe7fe Removed merge artifacts from HepMC Ascii writer