Shashlik out of time pileup mitigation

Multifit for ecal pulse shapes backport from 7_something, and PF pileup mitigation changes.  Includes #5845.

@bachtis, I had to add a change to class checksums
@lgray, @bendavid, FYI
@mark-grimes : `slc6_amd64_gcc472` as well. on top of CMSSW_6_2_X_SLHC_2014-10-21-0200.