Merge branch 'feature/stdvariant' into 'master'

ref:core/dune-common In dune-subgrid we wanted to use std::variant which is
part of C++17's STL ([see e.g. here]). Since the corresponding compilers (or
rather STL implementations) aren't too widespread by now and also out of pure
curiosity, I reimplemented std::variant myself using only C++14 and some of
Dune::Hybrid. In the end I ended up with a implementation that covers most of
the STL functionality and behaves more or less the same way (though it
probably won't be as safe, fast or complete as e.g. the gcc implementation, of
course). If this might be of any value for the Dune project, I'd be happy to
contribute this to dune-common.

See merge request [!342]

  [see e.g. here]: http://en.cppreference.com/w/cpp/utility/variant
  [!342]: gitlab.dune-project.org/core/dune-common/merge_requests/342

Merge branch 'minimum-vc-version-on-clang7+' into 'master'

ref:core/dune-common Close: [#132]

See merge request [!591]

  [#132]: gitlab.dune-project.org/NoneNone/issues/132
  [!591]: gitlab.dune-project.org/core/dune-common/merge_requests/591


Closes #132

This is to appease cmake 3.5.1 on Ubuntu 16.04

Close: #132

Merge branch 'fix-typos' into 'master'

See merge request [!589]

  [!589]: Nonecore/dune-common/merge_requests/589

Merge branch 'BitSetVector-add-documentation-and-implement-reset' into 'master'

See merge request [!588]

  [!588]: Nonecore/dune-common/merge_requests/588

They are not included in the generated API documentation otherwise.

Merge branch 'ci/fix-test-labels' into 'master'

See merge request [!585]

  [!585]: Nonecore/dune-common/merge_requests/585

All of the other modules don't specify the quick label on their tests.

Merge branch 'ci/centralize-config' into 'master'

See merge request [!584]

  [!584]: Nonecore/dune-common/merge_requests/584

The special vectorization test run stays in the local configuration, as it is specific to
dune-common.

Merge branch 'ci/clang-7' into 'master'

See merge request [!583]

  [!583]: Nonecore/dune-common/merge_requests/583

Merge branch 'feature/std-negation' into 'master'

ref:core/dune-common This implements c++17's std::negation in namespace
Dune::Std::

See merge request [!582]

  [!582]: gitlab.dune-project.org/core/dune-common/merge_requests/582

This implements c++17's std::negation in namespace Dune::Std::

Merge branch 'fix/test-target' into 'master'

See merge request [!581]

  [!581]: Nonecore/dune-common/merge_requests/581

Merge branch 'feature/dynamic-static-factorial-binomial' into 'master'

ref:core/dune-common Added some dynamic and static methods for calculating
factorials and binomials. There are several different implementation in
several modules of varying accessibility and age which can be replaced by
this.

See merge request [!471]

  [!471]: gitlab.dune-project.org/core/dune-common/merge_requests/471

[!576] [math] deduce the return value of Power in order to allow unit value types (see dune-grid#79)

Merge branch 'power-auto' into 'master'

ref:core/dune-common When working with unit value types (e.g. meters, seconds,
\...) the return type of Power is not the value type. This MR changes the
return type to auto to enable automatic type deduction.

See merge request [!576]

  [!576]: gitlab.dune-project.org/core/dune-common/merge_requests/576

Merge branch 'bugfix/self-assignment' into 'master'

ref:core/dune-common Indeed, isNaN could be something complicated, although
normally it just should be double.

See also [!573] and [dune-istl!235]

See merge request [!578]

  [!573]: gitlab.dune-project.org/NoneNone/merge_requests/573
  [dune-istl!235]: gitlab.dune-project.org/Nonedune-istl/merge_requests/235
  [!578]: gitlab.dune-project.org/core/dune-common/merge_requests/578

Indeed, isNaN could be something complicated, although normally it just
should be double.

Merge branch 'feature/prioritize-virtualenv-package-over-venv' into 'master'

ref:core/dune-common The venv packages cannot handle the system interpreter
being a virtualenv in itself - though this is not incommon. The commit just
prioritizes virtualenv and spits out warning if a user runs into the above
scenario.

This merge request supersedes [!559] after @smuething dislike for the former.

See merge request [!560]

  [!559]: gitlab.dune-project.org/NoneNone/merge_requests/559
  [!560]: gitlab.dune-project.org/core/dune-common/merge_requests/560

Merge branch 'feature/add-dunecontrol-cmake-command' into 'master'

See merge request [!574]

  [!574]: Nonecore/dune-common/merge_requests/574

Merge branch 'pivoting_switch' into 'master'

ref:core/dune-common As discussed in [!449], the user should be able to
disable pivoting if needed. This merge request is intended as a basis for
discussion and adds a simple static switch to DenseMatrix to disable pivoting.
Depends on [!449] and [!451], the only relevant commits for the switch are the
last two.

See merge request [!452]

  [!449]: gitlab.dune-project.org/NoneNone/merge_requests/449
  [!451]: gitlab.dune-project.org/NoneNone/merge_requests/451
  [!452]: gitlab.dune-project.org/core/dune-common/merge_requests/452

Merge branch 'let-cmake-disable-pkgconfig-search' into 'master'

For whatever reason we still allow to search for a module with pkg-config if
CMake was not successful. This leads to the weired situation that if we pass
-DCMAKE_DISABLE_FIND_PACKAGE_dune-uggrid=ON to cmake and dune-uggrid is
installed in a default sytem path we will end up with a CMakeCache.txt
actually using dune-uggrid.

This patch is the minimal change to stop searching for a DUNE module with
pkg-config if CMake was instructed not to use it.

See merge request [!569]

  [!569]: gitlab.dune-project.org/core/dune-common/merge_requests/569

For whatever reason we still allow to search for a module
with pkg-config if CMake was not successful. This leads to
the weired situation that if we pass
-DCMAKE_DISABLE_FIND_PACKAGE_dune-uggrid=ON to cmake and
dune-uggrid is installed in a default sytem path we will end
up with a CMakeCache.txt actually using dune-uggrid.

This patch is the minimal change to stop searching for a
DUNE module with pkg-config if CMake was instructed not to
use it.

Merge branch 'fix-typos' into 'master'

See merge request [!568]

  [!568]: Nonecore/dune-common/merge_requests/568

Merge branch 'test-output-iterators' into 'master'

See merge request [!567]

  [!567]: Nonecore/dune-common/merge_requests/567