cleanup user actions and MC truth

[civanch]

Added "primary" to the list of known processes (type=0) in Geant4 process enumerator.
Do not use CurrentG4Track - because it adds two thread local variables for nothing, instead allow direct interface from StackingAction to TrackingAction.

Should not affect results.

[cmsbuild]

A new Pull Request was created by @civanch (Vladimir Ivantchenko) for CMSSW_7_2_X.

cleanup user actions amd MC truth

It involves the following packages:

SimG4Core/Application
SimG4Core/Notification
SimG4Core/Physics

@cmsbuild, @civanch, @Degano, @mdhildreth, @nclopezo can you please review it and eventually sign? Thanks.
You can sign-off by replying to this message having '+1' in the first line of your reply.
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[civanch]

+1

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_2_X IBs unless changes or unless it breaks tests.

[cmsbuild]

+1
Tested at: ebcbd10
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-4803/498/summary.html

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_2_X IBs unless changes (tests are also fine).

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-4803/498/summary.html

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_2_X IBs unless changes (tests are also fine).