Automate the generation of trace.png and cutout.png files

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
• 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
• The script should have saved several .png files into the folder where the .brd file is