When using ADOL-C together with MPI we need to use different tags in the
ADOL-C function calls for each process. If we use the same tag, then the
processes will interfere with each other causing undefined behaviour.

This to clang for pointing out the problem.  I had not noticed it before
because the code was only wrong for dimworld<3, which I never tried.

This makes sequential cosserat-continuum compile again.

Added program to solve a combined minimization problem:
Minmize the sum of an elastic energy (representing the substrate)
and a cosserat energy (representing a thin film on the substrate).

This makes mixed-cosserat-continuum compile again.

But keep compatibility with dune-grid 2.6 as well.

WARNING: These methods implement the projection in quaternion
space.  This is NOT the canonical projection in matrix space.

The current implementation assign one degree of freedom to each
element, regardless of its type.  That only works for quad grids:
We are implementing Lagrange FE here, and these don't assign
degrees of freedom to triangles.

I found those wrong types when trying to use a HarmonicEnergyStiffness
with a RigidBodyMotion.

The latter is deprecated as of dune-functions 2.6.

It's the same code, but the old name is deprecated.

Running the test aborts with an error, because the error is exactly
the same as before this patch.