Add opus testcase

[prudhomm]

The opus testcase needs to be added to the toolbox benchmarks, we have some results to compare with in some cases (with Comsol)

[prudhomm]

@GQMP I would like you to be on the forefront of these developments.

[GQMP]

Where can I download the reference results ?

[prudhomm]

• OpusBenchmarkValidation.pdf
  I have also the tex files and everything I think

[prudhomm]

I just shared with you the opus benchmark via dropbox.
you can use pandoc to transform tex files into asciidoc files