add remaining bepi particles

[jgieseler]

• This PR adds support for ~1 MeV electrons and >25 MeV protons
• The channel(-combinations) for our analysis are now:

  channel = [2]    # 100 keV electrons
  channel = [5,6]  # ~1 MeV electrons
  channel = [8,9]  # >25 MeV protons

• No other combination of species and channels will work