Channel opt-out command

[Errolyn]

Add a command that will allow a user to opt-out of a channel something like !leaveChannel <channel-name> which would then remove read permissions for the user in that channel. This command should probably function via DM with an additional guild parameter. There should also be a equivalent join command to rejoin channels they have left.

There should be a check that their permissions rank is such that they should be able to see/join the channel.

If constraining to the correct permissions for the role is not available then this command should not be added.