help for return type.

[outscale-mgo]

--help ReadVms show all parameters arguments help, but we don't have return types explained.
Adding return type in the --help, could be slightly too verbose, so I guess we need either a new option, (--help-return) or a new argument to --help (--help --all ReadVms, --help --in ReadVms, --help --out ReadVms --help --brief ReadVms, --help --default ReadVms)