[!322] Use shared_ptr instead of raw pointers in construction of GeometryGrid

Merge branch 'feature/shared-ptr-in-meta-grids' into 'master'

ref:core/dune-grid Previously, raw pointer were used to pass the host grid to
geometry grid and ownership of the object was transferred. This commit
switches this to the more modern way of using a shared_ptr for this case. The
old constructors are deprecated.

This fixes [#86]

See merge request [!322]

  [#86]: gitlab.dune-project.org/NoneNone/issues/86
  [!322]: gitlab.dune-project.org/core/dune-grid/merge_requests/322


Closes #86