A few options aren't documented in the manpages. This commit adds
documentation for them based on the --help output and relevant commit
messages. Some of it could probably use more elaboration.
For a few commands the options aren't fully documented. This commit
makes the manpage documentation (almost) match the options shown
when you run "<command> --help" on the command line.
This adds --forbid-read, --forbid-write, --forbid-delete and
--forbid-grant-permissons options to flatpaks document-export
command, to let it revoke permissions on exported documents.
