Introduced intermediate interface layer between Geant4 UserActions and R...

Added intermediate interface layer between Geant4 UserActions and RunManager allowing to use the same UserActions for sequential and multi-threaded runs.

Updated EM physics of QGSP_FTFP_BERT_EML to be the same as in Geant4 10.0 distribution with only difference for electrons below 100 MeV.

This PR should not be merged to 7_1_X so far.