add PCB schematic files for hardware revision 6

Note to all the IKEAhackers:
Sorry guys for being so late but we got a little suprised when our article got immediately released after sending it into review. Before public release, we expected a "do you want to go online, now?"
So Fritz had to do some extra night shifts to get it ready for release as soon as possible.
Keep us up to date if you run in any trouble with these files (ikea@wylight.de)