cmake: add missing fix_omp.h and fix_omp.cpp to compilation

Add data duplication option to the KOKKOS package

[Feature Contribution] Scafacos

Collection of CMake fixes

cmake: only add tests if exe is build

Add core tests to CMake

Collected diverse small changes

recover some const'ness in Domain class, that was lost when merging MESSAGE package. fixes lib/atc compilation issue

new MESSAGE package for client/server/coupling

liblammps.pc: add lammps version

cmake: add FindLAMMPS.cmake.in