The code erroneously used std::tie to combine two local variables
to a single return value.  That may fail because std::tie produces
a tuple of references.  Once the method has returned these references
may or may not be valid anymore.  I am surprised that this bug
has not caused trouble much earlier.

Add dune-gmsh4 in the CI-script

See merge request !124

Use dune-gmsh4 to read in Gmsh files for cosserat-continuum-2d-in-3d-X-X

See merge request !123

In particular:
- Use the CosseratVTKWriter also for MIXED_SPACE = 1, only print out the deformation though
- Use a SubsamplingVTKWriter only for dim==gridDim==3

Use the grid function provided by the gmsh4-reader as the stressfreegridfunction in nonplanarcosseratshellenergy

This only works for gmsh-files with version 4 or 5, but this is what we want

Build with dune-fufem 2.8

See merge request !115

The multiplication by operator* between a ScaledIdentityMatrix
and a FieldMatrix only got introduced in Dune 2.9.  Therefore,
avoid it if we are building with earlier versions of Dune.

Fixes

See merge request !121

Add option to define deformation Dirichlet values for each direction separately in cosserat-continuum

Make GFE_ORDER and LFE_ORDER compiler macros and build the necessary combinations of cosserat-continuum-Xd-in-Xd

To build these combinations with the CI-system, install foamgrid for the tests with parmg, vtk, curvedgeometry and curvedgrid

This is needed to actually compare the 3D-model with the 2D-approximation

Correct the stopping criterion in the Riemannian-TR-Solver,...

See merge request !120

Deprecate the call to energy with a RigidBodyMotion in cosseratenergystiffness and in nonplanarcosseratenergystiffness - this is actually duplicate code!

They can't be removed yet because they are still used in tests though!

Correct the stopping criterion in the Riemannian-TR-Solver, Riemannian-PN-Solver and MixedRiemannian-TR-Solver

Do not stop if the correction gets small because the trust region radius gets small or the regularization parameter gets large

The modules dune-fufem and dune-matrix-vector
have been moved from the FU Berlin server to the server
operated by the Dune project when Carsten Gräser left
FU Berlin.

Correct the dimension of the rotation and the deformation in the...

See merge request !118