Add 2 new GenFilters for use by HI photon team

[harmonicoscillator]

These two gen filters for Pythia8 are meant to mimic the older ones used with Pyquen, which can be found here:
https://github.com/cms-sw/cmssw/blob/CMSSW_7_5_X/GeneratorInterface/HiGenCommon/src/EcalGenEvtSelector.cc
https://github.com/cms-sw/cmssw/blob/CMSSW_7_5_X/GeneratorInterface/HiGenCommon/src/EcalGenEvtSelectorFrag.cc

@bi-ran has done some sanity checking between the old filters and new filters which can be found here:
https://twiki.cern.ch/twiki/pub/CMS/MITHIGAnalysis2015/MCFilters.pdf

We would like to include these filters in the 75X series to be used for HI MC production.

[cmsbuild]

A new Pull Request was created by @richard-cms (R. Alex Barbieri) for CMSSW_8_0_X.

It involves the following packages:

GeneratorInterface/GenFilters

@vciulli, @covarell, @thuer, @cmsbuild, @bendavid, @davidlange6, @govoni can you please review it and eventually sign? Thanks.
@mkirsano this is something you requested to watch as well.
@slava77, @Degano, @smuzaffar you are the release manager for this.

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[covarell]

+1

[cmsbuild]

The tests are being triggered in jenkins.
https://cmssdt.cern.ch/jenkins/job/ib-any-integration/9922/console

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_8_0_X IBs after it passes the integration tests. This pull request requires discussion in the ORP meeting before it's merged. @slava77, @davidlange6, @Degano, @smuzaffar

[cmsbuild]

+1
Tested at: 50ad5df
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-12510/9922/summary.html

[harmonicoscillator]

Rebased on newest 8_0_X to avoid conflict with PythiaFilterHT

[cmsbuild]

Pull request #12510 was updated. @vciulli, @covarell, @thuer, @cmsbuild, @bendavid, @davidlange6, @govoni can you please check and sign again.

[covarell]

+1

[cmsbuild]

The tests are being triggered in jenkins.
https://cmssdt.cern.ch/jenkins/job/ib-any-integration/9995/console

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_8_0_X IBs after it passes the integration tests. This pull request requires discussion in the ORP meeting before it's merged. @slava77, @davidlange6, @Degano, @smuzaffar

[cmsbuild]

+1
Tested at: f666f5e
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-12510/9995/summary.html

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-12510/9995/summary.html