message: AliFemtoAnalysisPionPion: Implement Configuration builder struct
diff: static const double PionMass = 0.13956995;
  static const int UNKNOWN_CHARGE = -9999;
  +
  template<>
  struct Configuration<AliFemtoAnalysisPionPion> {
  - int foo;
  - Configuration()
  - : foo(123)
  - {}
  + TString name;
  + AliFemtoAnalysisPionPion::AnalysisParams analysis_params;
  + AliFemtoAnalysisPionPion::CutParams cut_params;
  - Configuration(AliFemtoConfigObject cfg):
  Configuration()
  + : name("PionFemtoAnalysis")
  + , analysis_params()
  + , cut_params()
  {
  - cfg.pop_and_load("foo", foo);
  }
  - operator AliFemtoAnalysisPionPion*() const {
  + Configuration(AliFemtoConfigObject cfg)
  + : name(cfg.pop_str("name", "PionFemtoAnalysis"))
  + , analysis_params()
  + , cut_params()
  + {
  + }
  +
  + operator AliFemtoAnalysisPionPion*() const
  + {
  + auto *a = new AliFemtoAnalysisPionPion(name.Data(),
  + analysis_params,
  + cut_params);
  return nullptr;
  }
  };
  