Faster Mobile Retinaface Versions Save

100% Python3 reimplementation of RetinaFace, a solid single-shot face localisation framework in CVPR 2020.

• Replaced CUDA based anchor generator functions with NumPy APIs.
• Stored runtime anchors via dict to avoid duplicate counting.
• Optimized NMS algorithm through vector calculation methods.
• Reduced FPN layers and anchor density for middle-close range detection.
• Used low-level Mxnet APIs to speed up the inference process.