First commit of porcupine board, not complete, not routed, don't use!
Schematic is stable, PCB mostly routed.
Fully routed design, needs checks, drill dwg.  Removed elink-north/south as these are now the same.
Completed design w/3-row XID/YID and various 4-pin IO connectors.
Fixed page ordering, changed "Mfr" field to "Manufacturer"
Will now re-do to combine all misc. functions onto a single 2xN connector.
Changed to a single header for all the PEC_POWER/misc. stuff.
Added 3D models for shrouded & right-angle connectors.
Ready for full review.