Use of `P` arrivals vs `S P` arrivals for location

Use of P arrival times for triangulation during location vs S-P arrival times.

We will use P arrivals for location using iLoc. (my interpretation) The S arrivals are still required for tomography. So the events need to be modified and saved in Seiscomp3 (possibly with a different eventId as we don't want to change the original recorded) with both the P and the S arrivals appened and associated.

For short distances (short travel times) use of S-P times can provide better location accuracy as in PhasePApy. However, for longer distances we should only use P arrivals for location.