Supply Converter channel reverting

[Maverick2797]

Sending the digiline message "off" to a supply converter reverts it back to the default channel (eg "supply_converter(x,y,z)"), and re-enabling it. It's like the node is being re-placed instead of being disabled

[h-v-smacker]

There is some backward-compatibility check that did it. I hesitated to throw it away, and I don't know exactly with which past configuration is has to deal, so I altered it. I think it should all be working now.