Add Exodus output support (with patch)

[Nico Schlömer]

Hi,

I sat down and put together a reasonably concise output handler for the ExodusII format, cf. http://www.osti.gov/bridge/purl.cover.jsp?purl=/10102115-8. The mechanism is based on the VTK library, so basically all of it is guarded by HAS_VTK.

In principle, the code first creates a vtkUnstructuredGrid data structure from the Dolfin mesh, then appends possible arrays (functions), and in a final step actually writes out the data.

I tested the code with a bunch of funny meshes and it appears to work alright.

It'd be good if you could have a look at the code and give some feedback here.

Cheers,
Nico

[Nico Schlömer (nschloe)]

Merge request sent. (Feel free to ignore the patch here.)