Add short hand aliases for named commands

[kradalby]

Add some handy aliases for commands, e.g.:

• namespaces: namespace, ns, user, users
• nodes: node, machine, machines, no
• routes: route, r
• apikeys: apikey, api
• preauthkeys: preauthkey, authkey, pre

Common subcommands:

• list: l, ls
• create: c, new?
• delete: del
• expire: exp, e

I think Cobra should support this, so should be relatively trivial to add.

Happy to take more suggestions :)

[e-zk]

I'm happy to work on this. Do we want all of these aliases or should I just pick a few from the ones you've listed?

I personally think it might be a bit unnecessary to have all of those aliases for nodes. Up to you though.