AthenaExamples: cmake configuration and package cleanup
Some housekeeping for the packages under Control/AthenaExamples
- remove
atlas_depends_on_subdirs
cmake statements - update link dependencies
- enable flake8 checking where relevant
- remove obsolete files
- remove two empty packages
- move private header files to src directory where relevant
- replace CLHEP/SystemOfUnits.h with the one from GaudiKernel