Implement command permissions system

[ShellyHerself]

designing a permissions system that we'll eventually use for chat commands and rcon.

A good way to differentiate between player commands, moderator commands, admin commands. Potentially also for things other than commands.

Something that can be sanely set up through commands and has sane defaults.

This also involves saving permissions to a file inside the Vulpes folder.

[Mimickal]

Depends on Zube #133