Cherry pick of "Merge branch 'AthAnalysisSetup' into 'master'" into the 1.0 branch
AthAnalysisExternals setup
See merge request !47 (merged)
As the next step, let's put the AthAnalysisExternals setup into the 1.0 branch. After which I'll need to update the AnalysisBase projects' externals to be in sync with LCG_88 before 1.0.13 should be tagged...