Created two new variables for THcDC, fNthits and fN_True_RawHits.

In tree they are called tnhit and trawhit.
Created two new variables for THcDriftChamber, fNthits and fN_True_RawHits.
In tree they are called tnhit and trawhit.
THcDC defined subdetector THcDriftChamber to have name Ch1 and Ch2 to do used in the tree.
THcDriftChamberPlane defined new method GetNRawhits to return fNRawhits for each plane.
Added member fNRawhits to THcDriftChamberPlane