channels need namespace

[MamiyaOtaru]

as of 1.13 all channels need to be of the form namespace:channel (and lowercase) or you get java.lang.IllegalArgumentException: Channel must contain : separator on both registering and unregistering. See https://wiki.vg/Pre-release_protocol#Plugin_Channels

an easy fix is checking each channel for lack of separator and prepending worldinfo: if needed, though of course clients will need to be aware of it (VoxelMap 1.14 is, though I'd be happy to change to whatever namespace someone decides on for a default if different). And I have no idea what if anything JourneyMap will use for a namespace in front of their world_info if they ever update to 1.13+