"wgd user --delete userId [userId ...]" option

[pbmarklf]

On https://github.com/pbmarklf/wgdev, my latest commit includes the "--delete" option for the "user" command to delete user(s) by their userId.

haarg, if you also think this is generally useful for WGDev, please add it when you can.

(I tried to make a pull request instead, but I'm still too much of a git newbie...)