Added function DetToLocal and LocalToDet used to consistanly go between

Added function DetToLocal and LocalToDet used to consistanly go between
Geant local detector coordinates (local) to the detector pad coordinates (det).
For example, xl,zl<->ix,iz for the pixels, xl,zl<->anode,timebucket for the
drifts, and xl,zl->iP,iN i,P/N-> xl,zl. Additionaly For the strips the function
Bool_t GetCrossing(iP,iN,&x,&z,c[2][2]). If this function is true then the
two strips cross within the sensitive volume of the strip detector. One other
new function has been added, Int_t GetNPads(). This function returns the
total number of posible digits/channels for the given segmentation. Additionaly
some comments have been added.