Continuous sTGC most probable arrival time

Update the characterization of the sTGC arrival time of electrons. The distance of closest approach is divided into 11 intervals. The 1st interval spans from 0 to 0.05 mm and the last three intervals are also 50-micron wide. The central region, from 0.05 mm to 0.75 mm is split into 7 intervals of 100-micron wide. A 4th-order polymonial is used to described the most probable arrival time. This update provides a continuous arrival time as a function of the distance of closest approach.