Mother/Daughter info in CMSFWLite reader

[Artur Lobanov]

I was trying to do some generator level studies using files produced by Pythia within CMSSW, and noticed, that DelphesCMSFWLite doesn't take over the mother / daughter information properly.
First, there is no M1/M2 info in the reader DelphesCMSFWLite.cpp at all.
And, second, the second daughter D2, is taken from the last daughter, not the second:
particle.daughter(particle.numberOfDaughters() - 1)
This is an important thing for Pythia, as it stores also the mother particle as the decay daughter, but with another status (2). That's why D2 was sometimes referring to the same mother particle.
In case of top decay, for instance, there are lots of gluons as daughters, so they get recorded as D2.

It would be nice to adapt this reader of CMSFWLite.

Thanks,
Artur