Import RecHit embedding code from CVS HEAD

Also, make it compile in CMSSW_7_0_X_2013-11-26-0200
Fix Zmumu skim
Switch off muon radiation correction by default
Don't apply the Zmumu skim by default

The default configuration is to run on a pre-skimmed sample. This is
more efficient when having to run over the same dataset many times, for
example when creating embedded samples for many different decay modes.
Remove unused file
Add new options of Ztautau replacer to MCParticleReplacer_cfi.py

This allows a configuration file generated with cmsDriver to work out of
the box.
Don't create embeddingKineWeights if no factors known for current configuration

This allows to run the code with configurations not used for the Htautau
analysis, for example mdtau=0. In those cases no embeddingKineWeights
are being produced (and a warning message is printed).

However, it is not a fatal issue. Maybe they are not needed, or if they
are they can be computed and applied still after the actual sample
production.
Fix multiple tauola decays for minimum visible transverse momentum cuts

It looks like between CMSSW_5_3_X and CMSSW_7_0_X the decay() function
of the TauolaInterface was changed such that it modifies the event
inplace instead of returning a new event. This commit adapts the code
accordingly.
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
Patch for TauSpinner rnd Check in 7_0_0_pre8
Provide RandomNumberGeneratorService for TauSpinner
Remove #warning about ZDCRecHit mixing

ZDC is not relevant for embedded tau samples
Remove EGamma/EGammaAnalysisTools from BuildFile.xml

The package is actually not needed at the moment.
Change INSTRUCTIONS file so that it can be run out of the box

Just doing `source INSTRUCTIONS'
Simplification of PrescaleService
Merged refs/pull/1651/head from repository cms-sw