Adding optional PU weighted neutral isolation to tau ID

Adding an option to run weighted neutral isolation for the tau isolation. The very same algorithm has been already implemented by #4131 for general use. As the tau isolation is calculated separately, it was necessary to implement this also within tau ID software.

The default RECO sequence is not affected, no changes expected.

The new option can be utilized via
```
--customise RecoTauTag/Configuration/addWeightedIsolation_cfi.addWeightedIsolation
```

The studies that show that this way of calculating isolation is superior to the previous ways of handling neutral isolation has been presented by Yuta at CPF: https://indico.cern.ch/event/322762/

Ok, good :) I was trying to do it at the time of writing the code, but I 
got stuck. Given that this is only temporary solution before going to 
"common lepton iso", I think it is good enough
On 11/09/14 16:13, StoyanStoynev wrote:
>
> In RecoTauTag/RecoTau/plugins/PFRecoTauDiscriminationByIsolation.cc:
>
> >        if ( filter(isoObject) ) isoCharged_filter.push_back(isoObject);
> >      }
> > -    BOOST_FOREACH( const PFCandidatePtr& isoObject, isoNeutral_ ) {
> > -      if ( filter(isoObject) ) isoNeutral_filter.push_back(isoObject);
> > +    if(!calculateWeights_){
> > +      for( auto const & isoObject : isoNeutral_ ) {
> > +	if ( filter(isoObject) ) isoNeutral_filter.push_back(isoObject);
> > +      }
> > +      isoNeutral_ = isoNeutral_filter;
> > +    }else{
> > +      for( auto const & isoObject : isoNeutralWeight_){
> > +	if ( filter2(isoObject) ) isoNeutralWeight_filter.push_back(isoObject);
>
> No, don't bother, I overlooked the difference... It certainly can be 
> further optimized/symmetrized in terms of code reduction but I am not 
> asking you to do it now, not obvious. Just think about that when you 
> have the time.
>
> —
> Reply to this email directly or view it on GitHub 
> <https://github.com/cms-sw/cmssw/pull/5255/files#r17422326>.
>

-- 
Dr. Pavel JEZ
postdoctoral researcher
Centre for Cosmology, Particle Physics and Phenomenology-CP3
Université Catholique de Louvain