[FEAT] Permissions backup/restore for a channel

[issy]

Overview

This would be useful when changing permissions in a channel, so you can effectively set a "restore point" for the channel in case you mess anything up with the permissions.

Commands

[p]permsbackup Save the permissions for the current channel
[p]permsrestore Restore the saved permissions for the current channel

DoD

• Permissions for a channel can be effectively restored, including all member and role permission overwrites

Stretch

• Copy and pasting permissions between existing channels
• Copy and pasting permission overwrites for roles in a channel (into the same channel)