Reorder staggered matrix

fixes #804 (closed)

TODO

• check tests

• write changelog

• Change matrix block arrangement for staggered models: The matrix block structure has been adapted such that it complies with the literature standard, i.e., having the velocity block on M[0][0] rather than on M[1][1]. This also requires re-arranging the submodels and properties in dumux-multidomain such that the face-related classes and vector entries now appear before the cell-centered ones. Backwards-compatibility can only be provided to a certain extent. The following changes need to made in the main file:

1.) change the order of the arguments for the assembler such that it reads:

auto assembler = std::make_shared<Assembler>(std::make_tuple(ffProblem, ffProblem, otherProblem, ...),
                                             std::make_tuple(ffGridGeometry->faceFVGridGeometryPtr(),
                                                             ffFvGridGeometry->cellCenterFVGridGeometryPtr(),
                                                             otherFvGridGeometry, ...),
                                             std::make_tuple(ffGridVariables->faceGridVariablesPtr(),
                                                             ffGridVariables->cellCenterGridVariablesPtr(),
                                                             otherGridVariables, ...),
                                             couplingManager,
                                             timeLoop, solOld);

// Not changing the arguments will yield a deprecation warning stating this hint but the code still compiles and runs.

2.) change the order of arguments in the partial function:

ffSol = partial(sol, ffFaceIdx, ffCellCenterIdx);

// Not changing the argument will rise a compiler error which makes the MR not fully backwards-compatible.