The previous code returned the energy dispersion as function of the base 10 logarithm of the energy. It is not really clear why this was the case, as the GCTAResponseIrf::edisp() class returns energy dispersion per MeV, and all high-level code assumes that energy dispersion is per MeV. Therefore, to avoid confusion and renormalization of energy dispersion information, also the GCTAEdisp2D::operator() now also returns the information per MeV.
The data is stored per migration bin, and hence a simple integration over migration should be unity for a give for a given offset angle and energy. The class was adapted so that this is now the case.
