[Tags] Add tags for dimension and codimension
Merge branch 'feature/FS1042-add-dim-codim-tags'

This branch adds simple structs that encapsulate a codimension or a
dimension and can be used to create overloaded function signatures. In
particular, they are required for the new support for range-based for
loops in dune-grid.

* feature/FS1042-add-dim-codim-tags:
  [Tags] Add tags for dimension and codimension