Introduces FSR flag and deprecates PHOTOS flag.
It closes [!9](https://gitlab.cern.ch/evtgen/evtgen/-/merge_requests/9) and [#9](https://gitlab.cern.ch/evtgen/evtgen/-/issues/9),
and is part of [T250](https://phab.hepforge.org/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.