Cleanup + Cosmetic changes

[haykh]

• AccExeSpace and aliases like that are changed to Kokkos::DefaultExecutionSpace
• removed explicit Kokkos flags inside local cmake
• ADIOS2 is now by default downloaded with Fetch_MakeAvailable
• improved reporting (added ARCH + DEVICES printing, plus paths to libraries) + TESTS when compiling with -D TESTS=ON
• removed explicit HDF5 dependency (still needed to compile ADIOS2), but not needed if ADIOS2 with HDF5 is already installed
• log level is now controlled from the input file (if log files grows too big, set log level to WARNING)
• minor warnings fixed