Neutron backgound: backport from 7_1_X

[civanch]

Added PhysicsLists and python fragments allowing neutron background study. It is a backport from 7_1_X.

[cmsbuild]

A new Pull Request was created by @civanch (Vladimir Ivantchenko) for CMSSW_6_2_X_SLHC.

Neutron backgound: backport from 7_1_X

It involves the following packages:

SimG4Core/Application
SimG4Core/Physics
SimG4Core/PhysicsLists

@cmsbuild, @civanch, @Degano, @mdhildreth, @nclopezo can you please review it and eventually sign? Thanks.
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@fratnikov, @mark-grimes you are the release manager for this.
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[civanch]

+1

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_6_2_X_SLHC IBs unless changes or unless it breaks tests. @fratnikov, @mark-grimes can you please take care of it?

[civanch]

+1

[mark-grimes]

merge

Tests 10000, 10200, 10400, 11200, 11400, 12000, 12400, 12800, 13000, 13600, 13800, 14000 and 14600 pass all steps.
Tests 12600 fails in step 2 with known errors.
Tests 12200, 14200 and 14400 fail in step 3 with known errors.