This is the name mandated by the dune-istl interface.

Deprecate the old name 'count'.

The dune-istl vector interface requires it.

Merge branch 'feature/test-amg-solverfactory-with-directsolver' into 'master'

ref:core/dune-istl Previously, we only tested with non-direct coarse solvers.
Now we do also test with them if the block type is not LoopSIMD.

The solver factory works without this being and is just not tested with direct
solvers in this case. @gruenich should decide whether to backport or not.

See merge request [!345]

  [!345]: gitlab.dune-project.org/core/dune-istl/merge_requests/345

Previously, we only tested with non-direct coarse solvers.
Now we do also test with them if the block type is not LoopSIMD.

Merge branch 'feature/non-const-solver-category' into 'master'

See merge request [!344]

  [!344]: Nonecore/dune-istl/merge_requests/344

* setSolverCategory is not allowed to alter a const value
* Adjust type of setSolverCategory's set
* Properly document deprecation of get/setSolverCategory

Merge branch 'feature/bump-to-2.8' into 'master'

See merge request [!342]

  [!342]: Nonecore/dune-istl/merge_requests/342

Merge branch 'issue/extra_semicolon' into 'master'

ref:core/dune-istl This is a small MR removing unnecessary semicolon after
some functions recently introduced by the solver creators. These semicolon
produce lots of compiler warnings when compiled with -pedantic

See merge request [!343]

  [!343]: gitlab.dune-project.org/core/dune-istl/merge_requests/343

Merge branch 'fix/solverfactory_parameters_of_default_iterative_solver_factory' into 'master'

ref:core/dune-istl ICC complains about using decltype(tl) in argument type
where tl is the first argument declared as auto.

See merge request [!341]

  [!341]: gitlab.dune-project.org/core/dune-istl/merge_requests/341

Merge branch 'bugfix/amg-tautological-compare' into 'master'

ref:core/dune-istl small fix t avoid compiler warnings and properly handle
range checking for potentially unsigned int values\...

See merge request [!339]

  [!339]: gitlab.dune-project.org/core/dune-istl/merge_requests/339

Merge branch 'fix/counter_overloads_namespace_clash' into 'master'

ref:core/dune-istl The namespace Dune::<unnamed>::Overloads collides with
Dune::Simd::Overloads and is not necessary as we are in an anonymous namespace
anyway.

See merge request [!340]

  [!340]: gitlab.dune-project.org/core/dune-istl/merge_requests/340

incCounter to DUNE_INC_COUNTER
getCounter to DUNE_GET_COUNTER

ICC complains about using `decltype(tl)` in argument type where `tl` is the
first argument declared as `auto`.

Merge branch 'feature/solverrepository' into 'master'

ref:core/dune-istl This MR introduces a solver factory that can assemble
solvers to a given LinearOperator, that are fully configurable via a
ParameterTree. It is based on a compile-time registry that can register class
templates at compile time. This compile time registry can then be added to a
ParameterizedObjectFactory.

We've introduced tree types of these Factories:

-   DirectSolverFactory
-   PreconditionerFactory
-   IterativeSolverFactory

We provide Macros for registering class templates. For example a
preconditioner can be registered like that:

    DUNE_REGISTER_PRECONDITIONER("ssor", default_preconditoner_BL_creator<Dune::SeqSSOR>());

where default_preconditoner_BL_creator<Dune::SeqSSOR>() could also be replaced
by a object that creates the preconditoner from a matrix and a ParameterTree.

The solver factory can then be used like this:

    std::shared_ptr<MatrixAdapter<Vector,Vector>> op = std::make_shared<MatrixAdapter<Vector,Vector>>(A);
    std::shared_ptr<Dune::InverseOperator<Vector, Vector>> solver = getSolverFromFactory(op, solverConfig);

where solverConfig is a ParameterTree containing a configuration tree:

    [CGWithAMG]
    type = cgsolver
    verbose = 1
    maxit = 1000
    reduction = 1e-5

    [CGWithAMG.preconditioner]
    type = amg
    iterations = 1
    relaxation = 1
    maxLevel = 10

It is planned to have a library "libduneistl" at some point that contains
preconditioners and solvers for the most often used template parameters.

See merge request [!312]

  [!312]: gitlab.dune-project.org/core/dune-istl/merge_requests/312

Merge branch 'check-mtbm-with-heterogeneous-nesting' into 'master'

ref:core/dune-istl Meaning: you need multi-indices of different length to get
the different scalar entries.

See merge request [!283]

  [!283]: gitlab.dune-project.org/core/dune-istl/merge_requests/283

Meaning: you need multi-indices of different length to get the
different scalar entries.

Merge branch 'fix/dont_use_deprecated_communication_headers' into 'master'

ref:core/dune-istl Unclear target: 2.7 or after the branching.

See merge request [!338]

  [!338]: gitlab.dune-project.org/core/dune-istl/merge_requests/338

Merge branch 'doc-prec-pre-apply-post' into 'master'

ref:core/dune-istl fixes [#67]

See merge request [!337]

  [#67]: gitlab.dune-project.org/NoneNone/issues/67
  [!337]: gitlab.dune-project.org/core/dune-istl/merge_requests/337


Closes #67

Merge branch 'make_matrixmarket_less_verbose' into 'master'

ref:core/dune-istl The matrixmarket functions send their output directly to
std::cout. This MR changes this to Dune::dverb.

See merge request [!336]

  [!336]: gitlab.dune-project.org/core/dune-istl/merge_requests/336

Merge branch 'fix-typos-in-comments' into 'master'

See merge request [!335]

  [!335]: Nonecore/dune-istl/merge_requests/335

with LoopSIMD