for flexibility in coupling.

 for the staggered coupling scheme

for the staggered scheme.

 VectorMatrixAssemble::assembleWithJacobian

Clang format run on near-the-header lines.

Happy New Year

 from the two classes of coupled term.

[Coupling] Changed the members of the coupled term,

 which only contains the solutions of the coupled equations.

In some processes (using non-local methods, for example)
the assembly is split in two parts: computation of local
quantities and actual (non-local) assembly (integration)
into the local matrices.

pointer to StaggeredCouplingTerm

added more documentations about the staggered scheme

 for the staggered scheme.

coupled terms.