Add pye3d support

[pfaion]

This PR adds a plugin for the pye3d pupil detector.

The plugin will only be loaded if pye3d is available. In this case, it will replace the default 3D pupil detector.
Please note that pye3d is distributed under a different license than Pupil.

Open Questions

1. Since the base class PupilDetectorPlugin abstracts away handle_events() and child classes only implement detect(), we generally do not have access to detection results of other detectors in detect().
   However, any 3D detector needs the 2D result. To increase confusion, the old 3D detector does not work with the 2D pupil datum, but with the raw binary blob. Pye3D on the other hand needs the 2D pupil datum. We should come up with a better way of passing this, maybe just give access to the events dict in detect()?

2. Should we merge this even if the integration is not yet fully complete? Theoretically, we can release this code, even if it does not yet have all features (e.g. freezing the eye model), as it won't be used without having pye3d available anyways. I think that's a great chance for working incrementally without having one massive feature branch in the end.

[papr]

I am getting this error when running the pye3d detector during post-hoc detection:

Traceback (most recent call last):
  File "/Users/papr/work/pupil/pupil_src/launchables/player.py", line 672, in player
    p.recent_events(events)
  File "/Users/papr/work/pupil/pupil_src/shared_modules/pupil_producers.py", line 422, in recent_events
    assert pm.PupilTopic.match(topic, eye_id=pupil_datum["id"])
AssertionError

P.S. it might be necessary to delete the user_settings_eye* files from your player_settings since the eye process tries to restore the legacy 3d detector if it was loaded in the previous session.

[papr]

Tested all pupil-related plugins. Works as expected.