Permission system

[onerandomusername]

Description

In order to manage commands and who is allowed to use what, there should be a custom permission system which can mutate the permission requirements for every command.

This should be somewhat easily doable with custom checks and a global bot check. https://discordpy.readthedocs.io/en/master/ext/commands/api.html?highlight=check#discord.ext.commands.Bot.check

Each command and cog, plus subcommands should be able to be modified who can run them. There should be defaults as decorators on each command or cog_command_check.

In addition, this system should work with interactions and slash commands, with the fork that is chosen as a result of #129

This depends on both #75 and #107