update to new ATLAS Extensions (with improved error message for missing...

update to new ATLAS Extensions (with improved error message for missing magnetic field map, and bump the version number

ATLASExtensions @ 847eee85

-Subproject commit 803a7fbcef5f18596a4e78487dd5650e64928dd0
+Subproject commit 847eee85219d34706d2f3099bafb9d961fe12ffc

cmake/GeoModel-version.cmake

 # Set up the version of GeoModel as a cache variable, so that other
 # sub-projects could use this value.
-set( GeoModel_VERSION "4.4.3" CACHE STRING
+set( GeoModel_VERSION "4.4.4" CACHE STRING
     "Version of the GeoModel project" )