Standardize headers and docstrings (#4417)

* Implement new headers

* Reformat 1

* Reformat 2

* Reformat 3 - math

* Reformat 4 - yaml

data/xView.yaml

@@ -1,4 +1,4 @@
-# YOLOv5 🚀 by Ultralytics https://ultralytics.com, licensed under GNU GPL v3.0
+# YOLOv5 🚀 by Ultralytics, GPL-3.0 license
 # xView 2018 dataset https://challenge.xviewdataset.org
 # --------  DOWNLOAD DATA MANUALLY from URL above and unzip to 'datasets/xView' before running train command!  --------
 # Example usage: python train.py --data xView.yaml