Updated Cherenkov detector code
We have added a new parameter hcer_tot_pmts = 2 in hcana.param file.
It is equal to total number of PMTs in Cherenkov detector. With this
update, the THcCherenkov coarse process is complete. We have Raw adc,
pedestal subtracted adc, number of photo electrons and hits histograms
in the output root file for gas Cherenkov detector.
Fix title of xp in global variables list
Remove some old commented out code.