Alias channel can be deleted directly, link stays behind

[S-S-X]

Deletion should not be allowed for aliases, instead /channel-unalias alias followed by /delete_channel alias should be required. Add deletion check and prevent channel deletion with message indicating that channel is actually alias to xyz.

[S-S-X]

Alternative would be to clean up alias when deleting channel. There's no real harm other than if aliased channel gets created again it will still be alias instead of individual/real channel.

[S-S-X]

I guess it would make sense to also cleanup and actually completely delete all alias channels if target channel is deleted.

[S-S-X]

No auto deletion after all, I think it would currently be too complicated. So switched to simple solution: active aliases cannot be deleted.

Hopefully ppl wont be removing linked channels all the time because they'll have to run 2 commands to delete channel. If automatic unlink and deletion should happen then API to delete channels should be added and there's really no reason push that in hurry to just skip one chat command and that only under very special circumstances.