Add Jpsi+2 trks modules for hlt

Add a producer and a filter in HLTrigger/btau, used in a Jpsi+2trks hlt path
Thank you Sara: you improved from minimum 10, maximum 12 if clauses per candidate to minimum 4 maximum - and mostly - 8 such clauses.
You can reduce them further (minimum 1, maximum - and mostly - 4, i.e.halving them) if you define a vector e.g
  std::vector <reco::RecoChargedCandidateCollection::const_iterator> mucand;
and
  if (tkRef == vertexTrksRefVec.at(iVec) ) {mucand.push_back(cand); iFoundRefs++; break}
(or any more elegant variation of it...)