Kidiff

Added
* Workaround for KiCad 8.0.4 new feature: draw black drill marks on technical layers

Added
* Workaround for KiCad 8.0.2 computing hidden text when the GUI enabled it

Added
* New mode "2color" where you can control the added/removed colors

Added
* Smarter cache: changing KiCad or --zones option invalidates the cache

Fixed
* KiRi mode for KiCad 5:
- Plotting the worksheet makes KiCad crash, disabled

Added
* Option to un/fill zones

Added
* Support to generate KiRi SVGs *Experimental* (--kiri_mode)

Fixed
* PNGs not removed when no diff and --only_different was specified