Refactor Likwid implementation
This MR addresses the comment by @veenboer in !37 (merged)
The Likwid implementation has been moved to LikwidImpl.h/cpp.
Additionally, I also provided the ability to give a custom event group to Likwid::Create
, so that one can customize the energy measurements by Likwid (for example, if we only want to measure the socket but not DRAM).