Merge branch 'feature/flexible_ctype' into 'master'

ref:extensions/dune-foamgrid

### Summary

This MR adds a template parameter ctype to set the coordinate type for the
grid.

### Details

Grid, Geometry and Entity are parametrized with a the coordinate type to allow
different floating point or number types.

See merge request [!64]

  [!64]: gitlab.dune-project.org/extensions/dune-foamgrid/merge_requests/64

Merge branch 'fix/compiler-warning-grid-ptr' into 'master'

ref:extensions/dune-foamgrid fixes [#15]

See merge request [!66]

  [#15]: gitlab.dune-project.org/NoneNone/issues/15
  [!66]: gitlab.dune-project.org/extensions/dune-foamgrid/merge_requests/66


Closes #15

Merge branch 'issue/loadbalance_return_type' into 'master'

ref:extensions/dune-foamgrid The function loadBalance() should return a bool,
not void.

See merge request [!65]

  [!65]: gitlab.dune-project.org/extensions/dune-foamgrid/merge_requests/65

Merge branch 'feature/implement-entity-type' into 'master'

ref:extensions/dune-foamgrid Implement the convenience function of the entity
interface to get the geometry type without constructing a geometry first.

See merge request [!63]

  [!63]: gitlab.dune-project.org/extensions/dune-foamgrid/merge_requests/63

Constructing a geometry to get the type is always more expensive if
you just need the type. This implement the more efficient interface.

Merge branch 'feature/insert-boundary-segment' into 'master'

ref:extensions/dune-foamgrid Has to wait for
[core/dune-grid!348] to be
merged.

See merge request [!59]

  [core/dune-grid!348]: core/dune-grid!348
  [!59]: gitlab.dune-project.org/extensions/dune-foamgrid/merge_requests/59

Merge branch 'cleanup/factory-remove-unused-data-member' into 'master'

See merge request [!62]

  [!62]: Noneextensions/dune-foamgrid/merge_requests/62

Merge branch 'bugfix/facet-vertex-invalid-this-pointer' into 'master'

ref:extensions/dune-foamgrid This solves the issue with the wrong leafIndex_
in the vertex_ array.

See merge request [!61]

  [!61]: gitlab.dune-project.org/extensions/dune-foamgrid/merge_requests/61

Merge branch 'feature/vertex-pointer-face-1d' into 'master'

ref:extensions/dune-foamgrid Instead of storing a nullptr and document
undefined behaviour we can actually store a this pointer and have perfectly
defined behaviour.

See merge request [!60]

  [!60]: gitlab.dune-project.org/extensions/dune-foamgrid/merge_requests/60

Instead of storing a nullptr and document undefined behaviour we
can actually store a this pointer and have perfectly defined behaviour.

Merge branch 'feature/sumouternormalerror-warning' into 'master'

ref:extensions/dune-foamgrid With upstream changes in [core/dune-grid!332] the
test now pass whereas before they were expected to fail due to the sum of
outer normals check.

Depends on [core/dune-grid!332] to be merged.

Fixes [#7]

See merge request [!58]

  [core/dune-grid!332]: gitlab.dune-project.org/core/dune-grid/merge_requests/332
  [#7]: gitlab.dune-project.org/NoneNone/issues/7
  [!58]: gitlab.dune-project.org/extensions/dune-foamgrid/merge_requests/58


Closes #7

Merge branch 'fix/geometryinoutside-1d-grids' into 'master'

See merge request [!57]

  [!57]: Noneextensions/dune-foamgrid/merge_requests/57

Merge branch 'fix/leafindexset-intitializer-list' into 'master'

See merge request [!55]

  [!55]: Noneextensions/dune-foamgrid/merge_requests/55

Merge branch 'feature/remove-foamgridentitypointer' into 'master'

ref:extensions/dune-foamgrid FoamGridEntityPointer is not needed. We simply
implement the dereference and equal functions for all iterators.

See merge request [!54]

  [!54]: gitlab.dune-project.org/extensions/dune-foamgrid/merge_requests/54