Use FSR name instead of PHOTOS and deprecate PHOTOS flag.
Summary:
Introduces FSR flag and deprecates PHOTOS flag.
It closes !9 and #9,
and is part of T250.
Updated internal function names to be getFSR()/setFSR().
Adapted new files for FSR to use new syntax.
Implemented use of neverRadCorr as originally intended.
Test Plan: Run FSR tests and compare with master.
Reviewers: tlatham, jback, kreps
Reviewed By: tlatham, jback
Tags: #evtgen
Differential Revision: https://phab.hepforge.org/D113