adding python script to create NAND flashes

[nerdyscout]

python nand_generator.py kioxia.json

this adds some new python script to generate NAND flash symbols in compliance to the ONFI spec It might make PR obsolete as no generic symbols are needed anymore. All future symbols can be defined in vendor.json, symbol templates are stored in *.part files which are compatible to regular kicad symbol file format.

As I am a rookie to python I am happy to include any improvements you have. This PR is currently in draft because the micron.json needs some improvements (consolidate some parts as alias), but first I would like to get some feedback if it is worth the effort. thanks!