Analysis Externals Update, master branch (2020.02.25.)

This is a collection of a number of things, primarily aimed at making AnalysisBase build/behave correctly on macOS.

The full list of changes in atlasexternals-2.0.58 wrt. atlasexternals-2.0.57 is (atlasexternals@2.0.57...2.0.58):

• Made the environment setup scripts work with path names containing spaces;
• Taught AtlasCMake how to handle the Apple Clang compiler/linker correctly;
• Suppressed some long-standing warnings with CMake 3.9+ on macOS.

At the same time I made some cleanup in this repository as well:

• The projects had version number all over the place. I updated them all to the same (22.0.10) version.
• Removed the usage of <experimental/array> from MuonStationIndex.cxx. Apple's compiler doesn't have that header anymore, and I couldn't see a reason why it should be included anyway.

Finally, to make the installed AnalysisBase release set up a correct runtime environment on macOS (or any other OS that provides Python 3 from the system), I had to set ATLAS_FORCE_PYTHON2=TRUE for the project. For now... We'll have to see later on how to properly enable the building of both Python 2 and 3 versions of AnalysisBase at the same time... 🤔

Pinging @krumnack.