Scripts for CR weights from dilepton and photon trees

Introduce new scripts to compute the CR weights (from dilepton and photon data with a ptmiss < 125 GeV cut) directly from trees, i.e. from outputs of DileptonTrees and PhotonTrees analyses.

Notice that in order to reproduce all the weights, it is still necessary to re-run the PhotonTrees analysis 2 times: one for computing pT weights, since it needs the data to be already reweighted for nvtx, and one for applying all the weights.

Currently, weights are stored inclusively for lepton categories (i.e. dilepton and dimuon merged). This can be easily changed, by simply adding more channels in the scripts.