[!802] [cmake] Do not set CMP0042 and CMP0054

Merge branch 'feature/adjust-cmake-policies' into 'master'

ref:core/dune-common\> We require CMake 3.1, they are always true.

See merge request [!802]

  [!802]: gitlab.dune-project.org/core/dune-common/merge_requests/802