Create assembler folder

See merge request !135

Divide the regularization parameter through the scaling parameter in the PN...

See merge request !133

Divide the regularization parameter through the scaling parameter in the PN solver instead of multiplying

In the PN solver, we add identity*regularization/scaling to the stiffness matrix.
This has two effects:
- make the system matrix positive definite
- penalize large corrections to ensure an energy decrease in each step

The regularization parameter is adapted if either the system matrix is not positive definite
if there is an energy increase. This works similar to the trust-region radius in the TR solver.
The correction must be inside the trust-region, this ensures there is an energy decrease
in each step.
For each component of the correction, the trust-region radius as well as the regularization parameter
is multiplied with a scaling factor, because the correction for the displacement works depends
on the grid size where the correction for the rotation does not.

To align the effect of the scaling parameter, we need to divide through the scaling parameter in
the PN solver and multiply with it it in the TR solver.

Add norm option to Riemannian trust-region and proximal-newton solvers

See merge request !131

Add setup method to Riemannian TR and PN methods

See merge request !130

Move all implementations of spaces into a dedicated directory

See merge request !128

... by LagrangeLocalFiniteElementCache.

Make EmbeddedGlobalGFEFunction a dune-functions function

See merge request !94

It run-time fails on the CI system for unknown reasons.
I don't currently have the time to spend more time debugging this.
Therefore, this patch simply disables the test and leaves a note.

Currently this test fails on the CI system with an obscure message
about not being able to write the tape to a file.  Maybe reducing
the complexity of the functional (by reducing the FE order) will
get us around that.  In any case I think testing with first-order FE
is just as thorough as with second-order ones.

It was apparently not used.

If you should ever need something like this in the future,
please use periodicbasis.hh from dune-functions.

This used to work A Long Time Ago, but the feature was removed
eventually.  Unfortunately, the code still used to build,
but failed to produce the correct result.  More recently,
some other commit in dune-functions apparently now leads to
a build failure when trying to call 'interpolate' for a
vector-valued function and a scalar basis.  This is nice!
It allows to catch errors earlier.

The old style has been deprecated for a long time, and is not
supported by dune-fufem anymore.

(In particular, the code discretizationerror.hh now requires
functions to satisfy the dune-functions function interface.)

In the wake of this, compute-disc-error.cc gets a number
of changes.  Let's hope I didn't screw up anything.

There are two important changes:  First of all, the new class implements
the `dune-functions` interface rather than the deprecated one based
on inheritance from `VirtualGridViewFunction`. Secondly, the new class
does not hard-wire geodesic interpolation anymore.  Rather, you can
give it interpolation classes which then govern how interpolation is done.

This change was long overdue.  It was now needed to make
gradient-flow.cc compile with the post 2.9 version of dune-fufem again.

Replace std::tie by std::make_tuple

See merge request !126

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