- atben/Makefile (gerbv), atusb/Makefile (gerbv): show also the back
solder mask layer
- atben/README-PCB, atusb/README-PCB: don't claim the back solder mask
is empty
- README-PCB: added imperial units for board thickness
- README-PCB: changed surface finish recommendation to prefer ENIG more
strongly
- README-PCB: removed instructions for Gerber file generation from
"interpretation of files section"
- README-PCB: mention common coordinate system origin