DRAFT: Test high energy showers

In this MR I have a pushed a branch with the radio_em_shower.cpp example that I am using to test high energy showers.

I think it is crucial for everyone to pitch in and identify where the crashes we see in higher energies come from. We do need higher energy showers to present to ICRC this summer, if we want to people to actually start trusting our showers.

Feel free to change the cuts in radio_em_shower.cpp as they are set to 1MeV for the em part, but keep in mind that we do need to be able to put realistic cuts for production (for radio we need cuts < 1MeV for example).

Let's use this thread to discuss updates.