Eventio

* Do not read timestamp of `History*`, in `__init__`. These objects do no longer have
a timestamp member, but their `parse` methods return a tuple of `timestamp, content`.

* Refactor `iact.ArrayOffsets` to use the version header field instead of guessing the number of columns.

* Improve printing of objects (`__repr__` shows Low-Level eventio info, `__str__` shows higher level object info, improved printing utils)

* Make sure all telescope descriptions are read in `__init__` of `SimTelFile`
* Several low-level code improvements, e.g. raising earlier if a big-endian file is encountered

* Fix missing laser calibrations and camera monitorings in `SimtelTelFile` for calibration events

* Implement zero suppression reading
* Implement calibration event reading in `SimTelFile`
* Implement reading of emitter particles created by the IACT extension with `-DSTORE_EMITTER`
* Implement reading of pixel trigger times
* Use more consistent variable names

Fixes

* `simtel.PixelList` had the wrong telescope_id / code, now fixed
* `simtel.ImageParameters` now has telescope_id set in `__init__`
* Added missing object imports in `simtel.__init__`, so all simtel objects should now be importable from `eventio.simtel`

Bugfix for reading certain simtel files.