Feature/telescope asymmetry

The proposed feature branch reads a DL2 file from LSTProd2 and calculates the energy asymmetry between every telescope pair. It is stored as a dictionary where the key is the pair of telescopes ij and the value the mean energy asymmetry, calculated through all the events of the relevant observation block, as (Ei - Ej) / (Ei + Ej)

Closes #172 (closed), #171 (closed), #173 (closed)