First prototype of ComboHypoTools

The ComboHypoAlg is calling ComboHypoTools after the multiplicity test. I made one abstract class (IComboHyoTool) and one concrete implementation that combines the elements and applies a Dr cut on the RoIs. It works for two case of the EmulationTest: both with one leg (2mu) and with 2 legs (2mu_2e). Many improvements are already commented in the code (with additional cleanup), but need further discussion, maybe during the HLT hackathon next week. Tagging @tbold, @tamartin