13 te v mc relvals pre8 re cycle 70x gf4

These changes are not urgent nor are bug fixeS; yet please have them included in whichever forthcoming release along 700 (pre4?) - so we keep the release consistent with what we're using for relval production.

Changes:
+ recycle for particle guns samples
+ treat halo and minbias @13 TeV consistently
+ introduce 38T_PostLS1 in step1; leave it commented out in subsequent steps => needs GEN-SIM from 
+ 620_patch1 to be consistently activated