A little code duplication in favor not to deal with pointers.

The matrices are not in use by any process.

 assembler member function.

 the staggered scheme

This is going to replace one part of the local_coupled_solutions
object.

Pass through the interface to avoid the coupled_xs
in the feature.

Eliminate two single-line functions.

Pass process_id to FEM::assemble calls.

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-tidy modernize-loop-convert check.

for flexibility in coupling.

 for the staggered coupling scheme

for the staggered scheme.