Support autoenvolved anchors from ultralytics

[Tomakko]

Closes #119. I tested it only with yolov5_darknet_pan_s_r40 a.k.a. yolov5s from ultralytics.

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Codecov Report

Merging #120 (c668d4c) into master (68d955c) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #120   +/-   ##
=======================================
  Coverage   83.54%   83.54%           
=======================================
  Files           8        8           
  Lines         784      784           
=======================================
  Hits          655      655           
  Misses        129      129           

Flag	Coverage Δ
unittests	83.54% <ø> (ø)

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[zhiqwang]

Thanks @Tomakko , LGTM.

[zhiqwang]

Hi @Tomakko , I've tested your your proposal, it works very well, I'm merging this PR, and it would be more better if you could sign the CLA here.

Thank you again for your contribution!