Previously, the rod3d code used a hand-implemented first derivative
of the rod energy, and FD for the second derivatives.  This patch
replaces this by ADOL-C for both first and second derivatives.
Advantages are:
* The code is much shorter, and easier to understand.
* The previous code contained interpolation formulae for
  first-order 1d geodesic finite elements.  This restricted
  rod problems to first-order GFE.  A follow-up patch will
  allow higher-order approximations.
* The new code runs roughly twice as fast.

GeodesicFEAssembler can replace it without problems.

As a first step towards getting rid of the RodAssembler class,
this patch moves the getStrain, getStress, and getResultantForce
methods to the RodLocalStiffness class.  I am not 100% convinced
that that is the best place for them, but I can't think of a
better one right now.

ADOL-C implements most standard math functions for its
'adouble' type, and they are not in the namespace 'std'.
dune-fufem contains a file adolcnamespaceinjections.hh
which imports some of these methods into the 'std'
namespace, but that is not the proper way to do it.
Rather, they should be found by argument-dependent
lookup (ADL), that is

  using std::sin;
  auto v = sin(x);

In the 'mixed' case the volume term was simply forgotten, and not
actually handed to the assembler.

It is very unlikely that somebody will use that ever again.

Rather than using a default file, which was the case previously.

Otherwise the program aborts for the usual mysterious reasons.

Stop using the deprecated class PythonFunction

See merge request !66

Allow assembler to get temporaries

See merge request !10

Fix neumann boundary in y z

See merge request !49

Migrate from dune-fufem to dune-functions bases

See merge request !48

This is currently the faster solver

Use GFE::LocalEnergy, GFE::LocalIntegralEnergy, GFE::SumEnergy (and delete GFE::SumCosseratEnergy).

Add localintegralenergy.hh and neumannenergy.hh, they assemble the energy for a single element and work with a CompositeBasis

These classes work similarly to Dune::Elasticity::LocalIntegralEnergy and Dune::Elasticity::NeumannEnergy,
where the ones in Dune::Elasticity with a power basis (for the displacement function) and
Dune::GFE::LocalIntegralEnergy / Dune::GFE::NeumannEnergy work with a CompositeBasis (for the displacement AND the rotation),
so the indices to access the different parts of the basis are different.

Enhancements

See merge request !61

Only compile geodesicfeassemblerwrappertest if the version of dune-elasticity is greater or equal 2.7

film-on-substrate uses a class of dune-elasticity that is not available in earlier versions

Add sumenergy.hh, this class assembles the a sum of energies for a single element by summing up the energies of each GFE::LocalEnergy.

This class works similarly to the class Dune::Elasticity::SumEnergy, where Dune::Elasticity::SumEnergy extends
Dune::Elasticity::LocalEnergy and Dune::GFE::SumEnergy extends Dune::GFE::LocalEnergy.

Correct typo in the calculation of the alternator tensor

See merge request !60

Change TargetSpace of GFE::LocalEnergy to be a variadic template and Change from Virtual Function to lambda function in cosserat-continuum

See merge request !57

    With this it will be possible to for the SumCosseratEnergy and the SurfaceCosseratEnergy
    to extend GFE::LocalEnergy, as they need multiple types of TargetSpaces.

Virtual Function is deprecated after dune 2.7.

Remove homegrown VTKReader, use dune-vtk instead

See merge request !58

Simon Praetorius' dune-vtk module has much better support for reading
and writing than my old hacks in dune-gfe.  Let's start adopting
dune-vtk for VTK I/O.

In this initial step, dune-vtk becomes a dependency of dune-gfe,
but only an optional one.  This may change.

Add a GeodesicFEAssemblerWrapper - it wraps a MixedGFEAssembler so it can be...

See merge request !55

Add a GeodesicFEAssemblerWrapper - it wraps a MixedGFEAssembler so it can be used like a GeodesicFEAssembler

The GeodesicFEAssemblerWrapper assembles the Gradient and the Hessian using the MixedGFEAssembler and then
resturctures them so they can be used with the normal RiemannianTRSolver.
This only works, if the FE spaces have the same order.

Enhancements

See merge request !53

The GeodesicFEAssemblerWrapper needs to access the MatrixType.

Also adjust CosseratEnergyStiffness and MixedGFEAssembler for the use with a CompositeBasis instead of a PowerBasis