Unify egammaOnlyFromRawFlags with egammaOnlyPreExec.py
requested to merge ATLAS-EGamma/athena:egamma_only_CA_doNotdoGeant_thining_like_old_style_CI into master
citest Egamma used egammaOnlyPreExec citest EgammaCAConfig egammaOnlyFromRawFlags
These are the option we will need for egamma ART anyhow. So do them here.
Edited by Christos Anastopoulos