Added 3D for AVX M620720, generated by script.

[cnieves1]

Datasheet: http://datasheets.avx.com/ethertronics/AVX-E_M620720.pdf
Source: easyw/kicad-3d-models-in-freecad#361

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Thanks for creating a pull request to contribute to the KiCad libraries! To speed up integration of your PR, please check the following items as you complete them:

• A screenshot of the model(s) aligned with KiCad footprints is very useful
• Was the 3D model(s) created in a mechanical modelling program?
• Source files (or scripts) have been contributed
• Step model submitted in 1:1 scale
• WRL model submitted in 1:2.54 scale
• 3D model alignment checked against KiCad footprint
• WRL model uses correct material properties
• Geometry check performed against mechanical models