Add first and last trajectory point in each subdetector

EDEPTrajectory should store information on the first/last trajectory point in each subdetector, if any.

Best place to fill in such info is the EDEPTrajectory constructor.

The information should be stored as an iterator to the wanted points in the trajectory_points_ vector.

A possible solution:

std::map<component, EDEPTrajectoryHits::iterator> last_points

std::map<component, EDEPTrajectoryHits::iterator> first_points

EDEPTrajectoryHits::iterator GetFirstPointInDetector(component)

EDEPTrajectoryHits::iterator GetLastPointInDetector(component)