Make Python package and print_structure

[zonca]

@maxnoe had already implemented most of the parsing of the higher level in Kaitai, and that is available in #1

@maxnoe @jpivarski Unless you have other recommendations, I was thinking about these next steps:

• Turn the repo in a proper Python package where the kaitai automatically generated module is a subpackage of.

• Implement the different types of Objects in the package so that we can reproduce what eventio_print_structure prints out, e.g.

  eventio_print_structure test_files/corsika_iact/one_shower.dat 
      RunHeader[1200]
      InputCard[1212]
      TelescopeDefinition[1201]
      EventHeader[1202](event_id=1)
      ArrayOffsets[1203]
      TelescopeData[1204](event_id=0)
        Photons[1205](array_id=0, telescope_id=0, n_bunches=382)
      EventEnd[1209](event_id=1)
      RunEnd[1210]

[zonca]

@maxnoe @jpivarski are the next steps suggested above fine?

[jpivarski]

Yes, I think it sounds great!

I think it's a good idea to maintain a separation between the generic Awkward-Kaitai Python package and an EventIO package that uses it. Similarly, there will be an SDSS package that uses the same generic routines. (It's good to have at least two dependents like this, to clarify what's generic and what's domain-specific on a case-by-case basis: "Do both EventIO and SDSS need this, or only one?")