First version of ArcFace and MTCNN

[benjisympa]

There are less landmarks and embeddings than tracking because tracking do a BACKWARD and FORWARD that the network doesn't detect sometimes. I replace the class Face but I let you integrate this version as you want in a new branch, with 2 files or a global interface to compare the different versions and implement new one (new Open-cv detector for example ?). Or I can update the pull request latter with a global interface. Thanks.