Add possibility to store pulse shape for cross-talk studies

Add possibility to dump to ntuple the pulse shapes for all cells close to high energy cells in layer 2 in order to perform studies of cross-talk pulse shapes. The aim is to reprocess the special 32-samples LAr data recorded early in 2018. This code is only used in dedicated LArCaf jobs to produce ntuples for LAr pulse shape studies. At the same time also small improvement to store pedestal subtracted ADC as float in the ntuple instead of integer.