Update the output format (events.txt)

* Add track vertex parameters to events.txt
* Remove the angles.
* Change the order a bit.
Print verbosity values.
Use references instead of copying.

In principle this increases performance, although in practice this is not the
bottleneck. Still, a good practice.
Add a small execution time measurement script.
Store store_tracks among the common variables.
If not storing tracks, do not open steam.

Writing to /dev/null is slow. Not opening the stream works as well
(all writes fail sliently) and is for practical purposes as fast as
removing the write statements entirely.