[PEPPo] PEPPO G4beamline v.1 release

[Serkan Golge]

This e-mail is for simulation lovers,

PEPPO G4beamline version 1 has been released and can be found here :

https://positron.jlab.org/wiki/index.php/PEPPo_Geant4_WG

If you check the simulation vs. data entries from ELOG, magnet 
optimization studies are in very well agreement between data and simulation.

"Important changes from the v.0"

1) Most importantly, the spectrometer map offset issue is solved 
(Almost). If you would like to use the spectrometer field map I 
provided, your T1 target should be positioned in negative X, negative Z 
of the Cartesian coordinate system. The beam should be traveling in 
positive Z.
2) S2 transmission solenoid magnet field map is updated.
3) Polarization of e-/e+ beam and spin tracking in vacuum is added.