Rename `level` arg of `settings.get_module_globals()` to `stack_level`
Rename `level` arg of `settings.get_module_globals()` to `stack_level`

This clarifies the purpose of the arg and matches the corresponding
renaming of `settings.derive_top_level_package_name()`'s `level` arg to
`stack_level`.

wylee/django-arcutils,PSU-OIT-ARC/django-arcutils,PSU-OIT-ARC/django-arcutils,wylee/django-arcutils