Add particle barcode, child info to flavor tagging truth label

This adds:

• The barcode of the truth particle that sets the truth label for the flavor tagging labeling. This will appear in DAOD_PHYS.
• Some information on the charm child of the same truth particle. This will only appear in flavor tagging derivations.

No previously existing outputs should change.

While the barcode has no direct use, it should be more reliable than element links when we want to establish whether a given b-jet came from a given truth particle. This is especially true in "Truth3" collections where the particles are copied around to multiple places and links are liable to break.

While I was editing the flavor tagging derivation code I made a few more changes:

• Removed a few files that don't seem to be used anywhere
• Cleaned up the code that adds aux variable lists: it had some weird syntax which (arguably) might be responsible for some past bugs
• Made some changes to make the truth labeling configuration code in ParticleJetTools work in AthAnalysis
• Added AntiKt4EMPFlowJets and AntiKtVR30Rmax4Rmin02PV0TrackJets to AllVariables in FTAG1.

As I said this shouldn't change any previously existing outputs, but I'm tagging @bdong, @ligang, @duperrin so they are aware.