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.

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.

Up until dune-common 2.7, the Dune namespace contained shared_ptr:
First as an actual implementation, later simply as a namespace
import.  Dune-common post-2.7 has removed that import,
and users of shared_ptr really have to explicitly specify
the std:: namespace prefix.

Do this by making RodAssembler more similar to the generic
GeodesicFEAssembler: the constructor argument is now a
general LocalGeodesicFEStiffness, and not something particular
to rod problems.

The predicates do implement operator(), so let's use that.

Because it really is only an energy.

Because it is not a stiffness, it is really just an energy.

Previously, they all inherited from LocalGeodesicFEStiffness,
which was weird, because none of them implemented first or
second derivatives as you would expect from something called
'stiffness'.