Fixed #20642 -- Deprecated `Option.get_(add|change|delete)_permission`.

Those methods were only used by `contrib.admin` internally and exclusively
related to `contrib.auth`. Since they were undocumented but used
in the wild the raised deprecation warning point to an also undocumented
alternative that lives in `contrib.auth`.

Also did some PEP8 and other cleanups in the affected modules.