This is a workaround for a bug that showed up after gitlab migration. See issue
infrastructure/issues0#62 for further discussion.

Merge branch 'cleanup/fix-compiler-warnings' into 'master'

See merge request [core/dune-istl!394]

  [core/dune-istl!394]: Nonecore/dune-istl/merge_requests/394

This reverts commit 0385deac.

Merge branch 'cleanup/remove-deprecated-solvecategory-interface' into 'master'

See merge request [core/dune-istl!390]

  [core/dune-istl!390]: Nonecore/dune-istl/merge_requests/390

Merge branch 'am2cmake' into 'master'

ref:core/dune-istl\> The last bits in dune-common were removed in
[dune-common!719].

See merge request [core/dune-istl!388]

  [dune-common!719]: gitlab.dune-project.org/Nonedune-common/merge_requests/719
  [core/dune-istl!388]: gitlab.dune-project.org/core/dune-istl/merge_requests/388

The last bits in dune-common were removed in dune-common!719.

Merge branch 'feature/require-cmake-3.13' into 'master'

See merge request [core/dune-istl!387]

  [core/dune-istl!387]: Nonecore/dune-istl/merge_requests/387

Merge branch 'feature/fix-broken-macro-guard' into 'master'

ref:core/dune-istl\> The loaction of the macro guard lead to the method test
not returning a value if neiter SUperLU nore SuiteSparse are found. While the
test is not executed in this case due to a CMake guard, these macro guards
should be placed in the correct place anyways for reasons of code hygiene.

See merge request [core/dune-istl!385]

  [core/dune-istl!385]: gitlab.dune-project.org/core/dune-istl/merge_requests/385

The loaction of the macro guard lead to the method `test`
not returning a value if neiter SUperLU nore SuiteSparse
are found. While the test is not executed in this case due
to a CMake guard, these macro guards should be placed
in the correct place anyways for reasons of code hygiene.

Merge branch 'feature/blocklevel-detection' into 'master'

ref:core/dune-istl\> Proposal for extending [!168] to MultiTypeBlockMatrix. As
the blockLevel for MultiTypeBlockMatrix is sometimes not uniquely determined
this proposed three functions minBlockLevel, maxBlockLevel and blockLevel. The
first two always work. The last one is only enabled if the first two return
equal levels. There is an additional function
`constexpr bool hasUniqueBlockLevel()` which checks this condition at compile
time.

Depends on the fix in hybrid utilities [dune-common!794]

See merge request [core/dune-istl!375]

  [!168]: gitlab.dune-project.org/NoneNone/merge_requests/168
  [dune-common!794]: gitlab.dune-project.org/Nonedune-common/merge_requests/794
  [core/dune-istl!375]: gitlab.dune-project.org/core/dune-istl/merge_requests/375

Merge branch 'feature/dont-require-fortran-for-arpack' into 'master'

ref:core/dune-istl\> dune-common does no longer require / look for Fortran, so
the condition would be always false.

See merge request [core/dune-istl!371]

  [core/dune-istl!371]: gitlab.dune-project.org/core/dune-istl/merge_requests/371

Based on the intial implementation by Oliver Sander (see !168)

dune-common does no longer require / look for Fortran,
so the condition would be always false.

Merge branch 'feature/cleanup_preconditioner_configs' into 'master'

ref:core/dune-istl\>

### Summary

This MR adds missing documentation for ParameterTree arguments and replaces
repeated constructors by delegating constructors.

See merge request [core/dune-istl!379]

  [core/dune-istl!379]: gitlab.dune-project.org/core/dune-istl/merge_requests/379

Merge branch 'issue/fcg_solver_constructor' into 'master'

ref:core/dune-istl\>

### Summary

Add missing constructor (with operator, precon, and parameter-tree) to
RestartedFCGSolver

### Details

The constructor with operator, precon, and parameter-tree, but without
scalar-product was just missing and is added by this MR for consistency with
all the other iterative solvers.

See merge request [core/dune-istl!378]

  [core/dune-istl!378]: gitlab.dune-project.org/core/dune-istl/merge_requests/378

Merge branch 'feature/direct_solver_constructors' into 'master'

ref:core/dune-istl\>

### Summary

Add ParameterTree constructors for direct solvers

### Details

To be consistent with other linear solvers, a constructor with a ParameterTree
argument is added to all direct solvers. Mostly the verbosity level is read
from the configuration, but SuperLU also reads the *reuseVector* parameter.

See merge request [core/dune-istl!377]

  [core/dune-istl!377]: gitlab.dune-project.org/core/dune-istl/merge_requests/377

Merge branch 'feature/replace-ifelse' into 'master'

See merge request [core/dune-istl!376]

  [core/dune-istl!376]: Nonecore/dune-istl/merge_requests/376