Pull Retina fitter from Massimo

Pull Retina fitter from Massimo Casarsa @casarsa
casarsa:RetinaFitter

Applied some changes:
- Revert fit_mode=0 to default
- Use xyPoint instead of TTHit for retina-related task
- Pass triggerTowerId and eventNum from fit() input parameters (for now)
- Set trigger tower to 27 (instead of 25) by hand