Fix minor issues

See merge request !89

Correct the sign of the Neumann and volume forces to make it consistent...

See merge request !84

Change nonplanarcosseratenergytest to make adaptions easier

See merge request !82

Remove commented out code in the surfacecosseratstressassembler

See merge request !85

Introduce python function for adaptive refinement

See merge request !86

With this, the preparatory stretching experiment for film-on-substrate can be done using dune-gfe.
The vertices for adaptive refinement can now be selected without specifying a shell area.

Correct the sign of the Neumann and volume forces to make it consistent throughout dune-gfe and dune-elasticity

In the energy file, the energies are *added*.
The Neumann and volume forces get the correct sign in the actual program file by mulitplying with (-homotopyParameter).

Fix error in surfacecosseratenergy

See merge request !81

The contravariant base vectors were not calculated correctly.
The contravariant base vectors are the *columns* of the inverse of the covariant matrix, not the rows.
To fix this, take the rows of the transpose of inverse of the covariant matrix.

WHITESAPCES for previous commit: Add the option to use the Riemannian Proximal Newton solver also for problems with dim = dimwold

Use cholmod if the dune-solvers version >= 2.8, use umfpack for older versions

added ProductManifold<...>

See merge request !70

Fix error in nonplanarcosseratshellenergy

See merge request !80

The contravariant base vectors were not calculated correctly.
The contravariant base vectors are the *columns* of the inverse of the covariant matrix, not the rows.
To fix this, take the rows of the transpose of inverse of the covariant matrix.

Add a simple test with a grid containing one element testing if the energy is invariant of the number of grid refinements.

Fix/rotational dirichlet values

See merge request !79

Fix the use of projection-based finite elements in cosserat-continuum

See merge request !78

Add multiplication of a ScaledIdentityMatrix with another FieldMatrix to the collection in linearalgebra.hh

The tests failed since the construction of values of ProductManifold<> in ValueFactory uses random entries between [0.9..1.1]. These are then used for the tests and are projected onto the manifold. 

To pass this tests it is needed to adjust several Taylor expansions and thresholds. For example this commit increases the threshold from `1e-4` to `1e-2` and adds more terms to the Taylor expansion. The reason for this change is explained in the following. 

The problem is, even if the tolerance `1e-4` is sufficient to have a correct function value within machine precision, it is not always sufficient to get correct derivatives since here we lose orders of correctness.

For  example of for sinc(x) we need to put the threshold at `1e-4` to get the correct function value if we use  `1.0-x*x/6.0` as approximation formula.

If we then use this formula within automatic differentiation or finite differences, e.g. the derivative algorithms  "sees" only the following formulas of the first and second derivative:

- Function value: `1.0-x*x/6.0`   This function is implemented
- First deriv: `-x/3.0`      This sees the derivative algorithms as first derivative
- Second: `-1.0/3.0`       This sees the derivative algorithms as second derivative

Obviously, this is the case if the function value is inside the region where the Taylor expansion is used.

If we use these functions to test the exactness of the derivatives we need to set the threshold to `x<1e-6` to get exact second order derivatives where the error is within machine precision. Therefore, for larger values `x>1e-6` the exact formula has to be used to get correct results. Unfortunately, in this range the exact derivative are already unstable.
E.g. the first derivative formula behaves already strange near `x=1e-4`.

Therefore,
to get a correct derivative value we need to switch to the Taylor expansion earlier (`1e-4`) to prevent using the unstable exact formula. But in this range the Taylor expansion is unable to reproduce an approximation error within machine precision.

I think the only way to fix this problem is to add more terms to the Taylor expansions. Since even if they seem to be sufficient in terms of function value, usually they are not sufficient in terms of derivatives.

For `sin(x)/x` a test ist at https://godbolt.org/z/T995hGec3 and for `acos(x)^2` https://godbolt.org/z/TG9E15jjf.

Cosserat-Continuum-Nonplanar

See merge request !72

Change the keywords for switching between the solvers to trustRegion and proximalNewton also in film-on-substrate