ThcCherenkov class.

Class for an Cherenkov detector consisting of two PMT's.
Fourth pull request. January 30 2014.
No need to cahnge the Map file.
New parameter hcer_tot_pmts = 2 is added to the hcana.param file
This code is for the coarse process of THcCherenkov class.
Names of all the variables are in lower case.

Variable Name   Description
phototubes      Nuber of Cherenkov photo tubes
adc             Raw ADC values
adc_p           Pedestal Subtracted ADC values
npe             Number of Photo electrons
npesum          Sum of Number of Photo electrons
ncherhit        Number of Hits(Cherenkov)