introduce NominalCollision2015 beamspot scenario, according to: https://indico.cern.ch/event/341218/
beamspot of postLs1 relvals set to NominalCollision2015; run1 relvals left as they were, making it explicit Realistic8TeVCollision (note: Realistic8TeVCollision is still the cmsDriver default)
UNDO: beamspot of postLs1 relvals set to NominalCollision2015
Merge pull request #5463 from franzoni/beamspot_NominalCollision2015-CMSSW_7_2_X_2014-09-22-0200

Beamspot nominal collision2015
Merge commit 'edf623e' into work

Conflicts:
	Configuration/PyReleaseValidation/python/relval_steps.py
Merge pull request #5677 from ktf/more-forward-port

Forward port #5463 into CMSSW_7_3_X