Update the atlasexternals version to 2.0.37
Update(s) since 2.0.36:
- Updated the standalone build of Python, Boost and FastJet(Contrib) to happen correctly in C++14/17 mode;
- Added Findhepmc3.cmake, FindNjet.cmake and FindOpenLoops.cmake to AtlasLCG.
Required for ATLINFR-3145.