HGCal PF Incrementals + Event display

[lgray]

This PR has:

• a simple version of Arbor clustering
• improved thresholds for PFRecHits
• HGCal in the event display

[cmsbuild]

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

HGCal PF Incrementals + Event display

It involves the following packages:

Fireworks/Calo
Fireworks/Geometry
RecoParticleFlow/PFClusterProducer
SLHCUpgradeSimulations/Configuration

@civanch, @nclopezo, @mdhildreth, @cmsbuild, @alja, @Dr15Jones, @StoyanStoynev, @slava77, @Degano, @ktf can you please review it and eventually sign? Thanks.
@alja, @bachtis 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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@fratnikov, @mark-grimes you are the release manager for this.
You can merge this pull request by typing 'merge' in the first line of your comment.

[lgray]

@pfs as discussed last week

[mark-grimes]

merge

Tested with 4 muons and pions. Only the known HGCal harvesting errors.