Fastsim data.vs.mc pu

fastsim pu scenarios for first data.vs.mc exercise

fastsim equivalent of https://github.com/cms-sw/cmssw/pull/4338/

call pu options in cmsDriver command as follows:
--pileup=E8TeV_2012_ZmumugSkim
--pileup=E8TeV_2012_run209148
--pileup=E8TeV_2012_run203002
--pileup=E8TeV_2012_run198588

these 4 new options were tested, generating 4 events.
true number of pu interactions was inspected visually