armarx-package: fixing package and library generation
This PR adds the following
-
the libraries are no longer generated in the 'libraries' folder but one folder upwards -
the UsePackage.cmake will no longer be generated. We don't need it anymore. -
the build folder will no longer be generated (incl. the .gitkeep file) -
minor fixes to the variant info generation (name + content) -
improved style of the top-level cmakelists