[!223] [SIMD] Use new ostream inserter.

Merge branch 'simd-io' into 'master'

Depends: [dune-common!551]

Addresses: [#50]

See merge request [!223]

  [dune-common!551]: gitlab.dune-project.org/core/dune-common/merge_requests/551
  [#50]: gitlab.dune-project.org/core/dune-istl/issues/50
  [!223]: gitlab.dune-project.org/core/dune-istl/merge_requests/223