### Summary ###

rename a sub-channel within a channel.

### IO ###

```[-ch_name (text) -sub_name (text) -new_name (text)]/[text]```

### Description ###

rename the sub-channel given in -sub_name for the channel given in -ch_name to the new name given in -new_name. the same rules for channel names also apply to sub-channel names. only the channel owner-level(1) and admin-level(2) is allowed to do this.