Previous commit introduced protection against uncommon (potentially
malicious) compression filters. This breaks restoring backups made with
a custom compression filter. Add an option to override this check, by
naming compression filter to use explicitly.
Most of them are moved from core-admin repository, even if tool is not
implemented yet. Some are generated using skel-manpage.py script.
This way we have complete man pages list, and sphinx will properly
warn/error about inconsistencies.
