The matrices are not in use by any process.

Similar to the central differences Jacobian assembler
but taking 1/3 time less.

From \dot{x} \approx (x - x0)/dt with a perturbation of
\hat{x} = x + \eps it follows that for consistency xdot
has to be perturbed with \eps/dt to keep the x0 unchanged.

Exemplary on SmallDeformationProcess, storage of dt
is no longer required and the assembly can be repeated
without dependency on the t/dt values.

Fixes multiple copyright messages in the doxygen docu.

ag '\\file' -L --ignore=ThirdParty *Lib |xargs  sed -i 's/\(.*\)\\copyright/\1\\file\n\1\\copyright/'

Clang format run on near-the-header lines.

Happy New Year

# remove #pragma once:
grep -r --include=*.h -Fx '#pragma once' -l . \
| while read f; do
    hg="`realpath --relative-to=. "$f" | tr '/.[:lower:]' '__[:upper:]'`"
    sed -i -e "/#pragma once/ c \\
#ifndef $hg\\
#define $hg
$ a \\
\\
#endif  // $hg" "$f";
done