Calib: Move fConvergenceFactor to base class TCCalib
Calib: Disentangle libCaLib from acqu_user libs
Calib: Addding fConvergenceFactor to energy gain calibration
User: Calib: Use photon energies directly, not the mean (variable names not changed though)
Calib: Use squared ratio of pi0 masses for energy calibration, according to Dominik's PhD thesis
Calib: Linear ratios converge better for uncalibrated gains

This reverts commit 3c3bdc2d5ecaf47bbbee8bd1796730277c5eb677.
Calib: Minor documentation fix
User: Calib: Quadratic energy correction might be broken anyhow, so use mean of photon energies

This reverts commit 1646cdcea36a5cadd03be3bb61c4db0ce9af8148.