Make MuonRadiationFilter work in CMSSW_7_0_X

Basically the pfPileUp and pfNoPileup modules now produce a
std::vector<edm::FwdPtr<reco::PFCandidate> > instead of a
std::vector<reco::PFCandidate>.
Add macros from Christian to create the kinematic reweights and validation plots
Update few files to Christian's private copy

which was advanced a bit since CVS HEAD.
Add INSTRUCTIONS file and simple addSpinWeight.py
Make muonRadiationFilter use original PFlow candidates