Add vtx smearing parameters: nominal beam parameters, realistic centroid

[rmanzoni]

back port of #10048

[cmsbuild]

A new Pull Request was created by @rmanzoni (Riccardo Manzoni) for CMSSW_7_5_X.

Add vtx smearing parameters: nominal beam parameters, realistic centroid

It involves the following packages:

Configuration/StandardSequences
IOMC/EventVertexGenerators

@cmsbuild, @civanch, @franzoni, @mdhildreth, @davidlange6 can you please review it and eventually sign? Thanks.
@ghellwig, @makortel, @GiacomoSguazzoni, @rovere, @VinInn, @Martin-Grunewald, @cerati, @dgulhan this is something you requested to watch as well.
You can sign-off by replying to this message having '+1' in the first line of your reply.
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@Degano you are the release manager for this.
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[civanch]

please test

[cmsbuild]

The tests are being triggered in jenkins.

[cmsbuild]

+1
Tested at: d6f5265
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-10051/44/summary.html

The following merge commits were also included on top of IB + this PR after doing git cms-merge-topic:
2fcaea4
7a8ff1c
6fab1b8
0156bbb
6c999d9
You can see more details here:
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-10051/44/git-log-recent-commits
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-10051/44/git-merge-result

[civanch]

+1

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_5_X IBs once checked with relvals in the development release cycle of CMSSW (tests are also fine). This pull request requires discussion in the ORP meeting before it's merged. @davidlange6, @Degano, @smuzaffar

[davidlange6]

+1