create documentation for zfs-toolbox

[igeo]

I think a basic documentation is needed for people to use this toolbox. Currently, a user has to read the code to see the usage and figure out the behavior by reverse engineering.
Thanks

[joelweinberger]

That's a great point, and we definitely want to do that. For now, each of the scripts does have a help flag ("-h" or "--help") that gives the usage and some basic help information, but we definitely ought to create more comprehensive documentation at some point.