qfn.fpd: corrected center pads, and general cleanup
qfn.fpd: corrected center pads, and general cleanup

- qfn.fpd: package names now also include the variant (for now: SiLabs,
  VHHD-2, or VHHD-6)
- qfn.fpd: inlarged center pad of QFN28-SiLabs (was QFN28) from 3.25 mm
  to 3.3 mm
- qfn.fpd: reverted QFN32-VHHD6 (was QFN32) to original geomtry
- qfn.fpd: introduced QFN32-VHHD2 for the ATmega32U2
- qfn.fpd: distribute solder paste in little islands (in progress)
- qfn.fpd: deleted stray unused vector in root frame

cfriedt/ben-wpan,cfriedt/ben-wpan,cfriedt/ben-wpan,cfriedt/ben-wpan,cfriedt/ben-wpan,cfriedt/ben-wpan