This is an issue from the [March 2017 PDELab Meeting](https://dune-project.org/community/meetings/2017-03-pdelab/). Entity sets can be removed from PDELab as soon as they are in core dune. They need to stay as a concept though(?). There is built-in `MCMGMapper`-functionality in the `IndexSet` which needs to be removed. This depends on #89.