Correctly register commands

[AL1L]

Although there's no easy way to do it, we need to register the commands correctly in Bukkit with tab complete and everything so that it doesn't show up as red and unknown command. To support more versions, we can use the current system as a fallback.

[andriemc]

They've added this already.

[connerdouglass]

Registering commands is supported by adding them to your project package.json file, like this:

{
    "commands": {
        "gmc": {
            "description": "sets your gamemode to creative"
        }
    }
}