First working version of centroid panelization

- Each Job in the gerbmerge cfg file can
  now have a centroid layer defined as
  follows: Centroid=%(prefix)s.SMD
  The centroid data is in the format
  RefDes,Layer,LocationX,LocationY,Rotation

- Currently this data is read in for each
  Job, rotation is applied to X, Y and the
  chip Rotation information as needed and
  then the new centroid data is just
  printed to the console as python lists.

- Right now there are fudge factors hard
  coded in job.writeCentroid method because the
  origin of the eagle file where our
  surface  mount centroid data is generated
  from is sligtly off compared to the generated
  source layer files that gerbmerge reads.