Merge pull request #572 from smuzaffar/IB/CMSSW_6_2_X/stable

create build-errors file in case compilation failed
move to pythia8 185
Update sherpa to verision 2.1
Merge pull request #598 from mkirsano/topythia8185_62X

move to pythia8 185
Merge pull request #607 from degano/sherpa_210_62X

Update sherpa to version 2.1
updated config and SCRAM verisons