DIC challenge data as tutorials and tests

[PolymerGuy]

The "DIC challenge" from the SEM (Society of Experimental Mechanics) community should be included as a demo and a part of the test suite. This could also be included as excellent tutorials. The datasets are found here: https://sem.org/dicchallenge And their paper with initial results are found here: https://link.springer.com/article/10.1007/s11340-017-0349-0

Suggestion:

• Add the analyses as demo-files complete with a comparison to the "correct" values
• Include these files as tutorials in the docs
• Include these files as a part of the test-suite