So far, the Cosserat rod energy implementation hat a first-order
finite element space hardcoded.  This patch removes that restriction.
As for the other models in this Dune module, the finite element basis
is now a template parameter of the model energy, and can be set to
any reasonable basis.

It is not a 'stiffness' anymore, but really only implements the
energy.

This is a prerequisite to a) support for higher-order FE,
and b) getting rid of the hand-written CosseratVTKWriter.

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.

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.

When dune-curvedgeometry is not found, the normal Derivative is set to zero.

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

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

Virtual Function is deprecated after dune 2.7.

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.

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

This is where they actually belong, create an own file for identity-dirichlet-values;
before we 'abused' a copy of the file cantilever-dirichlet-values.py

Then each process knows the initial stress free configuration and
can assemble its own part of the grid.

Do not call loadBalance() after each refinement.

Print out assembly time for each process on each process and
print out the gradient norms only on one process.

Add option to read in a displacement file that will be used for the stress-free configuration of the shell elements
When startFromFile is set to true, then the stress-free configuration is read from the given file - this file needs to match the *finest* level of the grid
When startFromFile is set to false, the stress-free configuration can be given in as a function

In 3D and for second order elements the globaldofmapper from dune-parmg is needed.