Refine measurements
Updated the velocity and stop times data structures to be indexed by pairs of sensors, e.g. get the velocities and stop time on the section of track D13 -> B2
. If values do not exist for a pair of sensors, it initializes the average velocity and stop time for that train.
TODO: update this data structure such that if values do not exist, it checks if values exist for the segment of track in reverse. If so, it initializes to those values instead of using averages.
Also, we need new measurements for the stopping times.