[PATCH] samba-tools: add computer subcommand

[joeg at catalyst.net.nz]

Hi Team,

I added a new `computer` subcommand for samba-tools, which has the same
set of commands as the `user` command, but work for a computer. Most of
the code are copied from user command and then adjust for computer.

Review appreciated!

Thanks, Joe.

-- 
Joe Guo
joeg at catalyst.net.nz
Catalyst IT