Train from --data path/to/dataset.zip feature (#4185)

* Train from `--data path/to/dataset.zip` feature

* Update dataset_stats()

* cleanup

* cleanup2

data/Argoverse.yaml

@@ -1,6 +1,6 @@
 # YOLOv5 🚀 by Ultralytics https://ultralytics.com, licensed under GNU GPL v3.0
 # Argoverse-HD dataset (ring-front-center camera) http://www.cs.cmu.edu/~mengtial/proj/streaming/
-# Example usage: python train.py --data Argoverse_HD.yaml
+# Example usage: python train.py --data Argoverse.yaml
 # parent
 # ├── yolov5
 # └── datasets