command option to print hierarchy

[jesteria]

(Optionally-enabled) (manage) command/option or other tool to print command hierarchy, like tree, (with descriptions and/or argument signatures).

For example:

$ manage server --help-tree
manage server    manage servers
|– user          manage users via ansible
|  |– add        add user logins
|  |– delete     mark logins for deletion
…

Above, the --help-tree option operates like --help, immediately printing a description of the hierarchy and exiting.

This could be offered by the manage command, but not enabled by default for other commands that make use of argcmdr; rather, for these, it should be easy to add or enable.