TauAnalysisTools: Use data handles in BuildTruthTaus

Hello,

The main goal of this MR is to replace direct access from evtStore with read/write handles, to allow derivations to run in MT (ATLASG-2528). This is located in BuildTruthTaus. I dropped a few deprecated functionalities, in particular WriteTruthTaus=0 which was building truth taus and keeping them in memory without registering them to SG. I also changed the behaviour of truth tau building. Before, if TruthTaus were not present in the input file, BuildTruthTaus would trigger truth tau building from TruthParticles. Now, BuildTruthTaus will always run truth tau building, unless it is put in "truth matching mode" by the TauTruthMatchingTool, in which case it will read the existing TruthTaus and apply truth matching to reconstructed TauJets.

This is a first step, the BuildTruthTaus+TauTruthMatchingTool design is still somewhat unfriendly and should be further improved.

The MR was tested on 1000 TRUTH3 events and 500 PHYS events, it doesn't change the output.

Cheers, Bertrand