Fix bugs in EgammaTrackParticleThinning and add GSF track thinning to PHYSLITE
This MR adds e/gamma GSF track thinning to PHYSLITE, reducing size/evt by a factor around 2 for GSFTrackParticles container, as discussed in https://its.cern.ch/jira/browse/ATLASG-2367
In addition, a few bugs in the underlying EgammaTrackParticleThinning tool are fixed that prevented the tool to keep only the selected GSF tracks without touching the InDetTrackParticles (in PHYSLITE these are kept from other domains when needed from them.)
Edited by Christos Anastopoulos