Correcting examples and tests
Summary:
- createGroupsFromMeshData called internally
- wrong field names for dumpers
- getForce deprecated
- material parameters not always correct
- some minor changes
Test Plan: run the tests & examples
Reviewers: #akantu-developers, richart
Reviewed By: #akantu-developers, richart
Differential Revision: https://c4science.ch/D197