Automate generation of trace and cutout .png

Matt Keeter wrote a Python script that opens up Eagle and exports a number of pngs using ImageMagick.

To get this script to run, use the following steps:

• Save eagle_png.py into the folder where you keep your .brd and .sch files
• Install (ImageMagick)[https://www.imagemagick.org/script/index.php]
• Create a polygon over your .brd design on the Milling layer (number 46)
• Save your .brd file and close Eagle
• Run eagle_png using the following command $python eagle_png.py board_folder/board_name.brd