Externals Update, master branch (2019.12.16.)

This is to update to atlasexternals-2.0.49. The list of changes wrt. atlasexternals-2.0.48 is (atlasexternals@2.0.48...2.0.49):

• Now building the GeoModelCore and GeoModelIO projects instead of the "old" GeoModelKernel (thanks to @rbianchi);
• Updated to FastJetContrib 1.041 (cherry-picked from the 1.0 branch);
• Implemented more explicit log filtering rules for atlas_add_test(...) (thanks to @fwinkl).

The second and third things in the list should be harmless. The FastJetContrib update was tested in 21.2 to some degree, and Frank's CMake update only adds some new features.

It is the first one that is a bit more of a suspect. 😛 I updated all packages that directly depend on GeoModel, with the following list of commands:

git grep -l "find_package( GeoModel" -- "*/CMakeLists.txt" | xargs sed -i "s/find_package( GeoModel/find_package( GeoModelCore/g"
git grep -l "GEOMODEL_INCLUDE_DIRS" -- "*/CMakeLists.txt" | xargs sed -i "s/GEOMODEL_INCLUDE_DIRS/GEOMODELCORE_INCLUDE_DIRS/g"
git grep -l "GEOMODEL_LIBRARIES" -- "*/CMakeLists.txt" | xargs sed -i "s/GEOMODEL_LIBRARIES/GEOMODELCORE_LIBRARIES/g"

I was even trying to update the copyright statements of the files, but none of them had one in them. 😛

Of course I didn't do a full build of Athena to test the changes, but I did build a few random "GeoModel packages". Those all built without a hitch, so hopefully this was enough to update the repository...