BUG: fixes bug T2542 and reintroduced a broken test
Summary:
closes T2542 and reintroduces the direct comparison between
MaterialLinearElastic1 and the de Geus reference implementation.
Test Plan: Jenkins
Reviewers: afalsafi
Reviewed By: afalsafi
Maniphest Tasks: T2542
Differential Revision: https://c4science.ch/D235