Move PCA pos calc into plugins

[lgray]

Avoids problem reported by Gaelle that was causing a plugin to get loaded twice.
Matrix test pass now in my local area.

@boudoul

[cmsbuild]

A new Pull Request was created by @lgray (Lindsey Gray) for CMSSW_6_2_X_SLHC.

Move PCA pos calc into plugins

It involves the following packages:

RecoParticleFlow/PFClusterProducer

@cmsbuild, @cvuosalo, @slava77 can you please review it and eventually sign? Thanks.
@mmarionncern, @bachtis this is something you requested to watch as well.
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@fratnikov, @mark-grimes you are the release manager for this.
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[cvuosalo]

@cmsbuild please test

[cmsbuild]

The tests are being triggered in jenkins.

[mark-grimes]

Tested privately along with #10156, tests 14062, 15662, 17662 and 17000 all fine (standard HGCal and a few arbitrary HGCal de-scope scenarios, only 2 events with 17000 since 140 pileup takes aaaages). Small problem with 17800 but that's (EDIT - ..not..) down to this PR (see discussion on #10156). Happy to merge but might as well wait for the automatic tests to come back, although I need to update the test numbers for those.

[mark-grimes]

merge

I'm happy from private testing (described above) that everything is okay. Need to get the release out and most of the automatic tests are for different scenarios.

[cmsbuild]

+1
Tested at: c993672
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-10152/122/summary.html