Fixes persistence of cleanup user groups after a group deletion.
Remove code (incl. tests) that has been marked as deprecated since (at least) Kotti 0.8.
Remove unused imports, no longer existing console_scripts and no longer needed dependencies.
Fix imports from deprecated modules to use the right location.
Re-add missing import (don't understand why that one's needed).
Merge pull request #322 from castaf/fix_cleanup_user_groups

Fixes persistence of cleanup user groups after a group deletion.
Merge pull request #350 from disko/feature/335_remove_deprecated_code

Feature/335 remove deprecated code.  Resolves #335.