- for CAE formats such as abaqus, nastran, starcd, etc, the element id
  is already part of the output format itself. For these cases, there
  is no use in generating an additional "Ids" field.

ENH: add code to ignore negative face ids

- these will arise from very special cases, such as when a
  solid element and side are encoded into a single integer.

BUG: starcd surface values output did not use original face ids