Calculation of the event-wise asymmetries

Implement the functionality that will analyse DL3 data, iterate over its events and produce histograms with the pair wise asymmetries of all participating telescopes within a distance.

The asymmetry is defined as a_ij = (x_i - x_j) / (x_i + x_j) for telescopes i and j, and x is the reconstructed energy by the corresponding telescope.

The initial algorithm produces histograms with the pairwise asymmetries that are saved in a ROOT file. We can replace ROOT with numpy or stop using histograms at all, TBD.