Reorganize project directories

[MedericFourmy]

For now, happypose main folders are divided in :

• happypose
  • happypose
  • toolbox
  • pose_estimators
    • megapose
    • cosypose

2 important functionalities should be put in common in my opinion:

• both megapose and cosypose contain very similar code for object 2D detection (a MaskRCNN interface)
• cosypose contains a multiview pose estimator that is agnostic of the single-view pose estimator

My proposition (debatable):

• happypose
  • happypose
  • toolbox
  • pose_estimators
    • megapose
    • cosypose
  • detectors
    • maskrcnn
    • cnos (to add)
  • multiview

With this approach, cosypose/megapose folder would contain only the pose estimation related code (as well as examples, evaluation, training etc.).

[MedericFourmy]

We could think about where to put depth refiners as well.

[nim65s]

I think this would be nice, but really breaking. So maybe we should get v1 first, maybe v1.1 after that, and then make this move for v2

[MedericFourmy]

For single-view pose estimation I'm not sure it would be that breaking. The high level interface to both single view pose estimtors is their respective cosypose PoseEstimator and megapose PoseEstimator. These classes would not change place or API, just some import paths to load the detector and depth refiner would change. If there is code somewhere that directly imports the detector/depth-refiner then yes it's breaking for them.