ENH: add basic handling for abaqus files (#1600)

- reads/write shell elements
  Output elements are "bunched" according to type and their set, but
  does not perform any reordering.

- can read solids, but extraction is not implemented.
  Simply ignore *Surface until that is resolved.

WIP: abaqus surface sampled output

- supports geometry scaling and field-specific scaling.

- separate geometry and values.
  Values are dumped in column format (raw) for scripting until
  things are finalized.