Allow specifying a port for digilines messages to be sent from the lua_controller

[oversword]

This allows a player to change the rules that are used to send the digililines message from the luacontroller by passing the port as the third argument to digiline_send

Specifying the port will send the message to the node neighbouring the port, as well as the nodes above and below that.

[Desour]

This has been requested once, but was denied due to digilines being intended to be position independent:
minetest-mods/digilines#37 (comment)

[oversword]

digilines being intended to be position independent

Yeah, that's dumb. It's an optional feature, you don't have to use it, and it's main purpose is to prevent talk-back like you mentioned in your comment, which is a serious issue with the way it currently works, and channels are not a solution.

abstract mesecons away from from the physical layout of the schematic

What you want to do is define your ports & pins at the top of the script then change them per location

[eshattow]

It would be really nice to be able to connect digiline to the node below the luacontroller / ioexpander. Burning a mesecons i/o port to connect with digiline is too limiting. The way around that limit is mesecons+digiline conducting pipeworks tube (but that is not possible in many situations). Another take on this would be to have mesecons ports connect on the same Y-height as the controller but have digiline connect at Y-1 perhaps with some sort of "microcontroller socket" that can bus the digiline signals from any luacontroller/ioexpander node above it? Already there's some trouble with digiline filter injector not accepting digiline conducting pipeworks tube from Y+1. Saying that digiline is intended to be position independent is not quite what happens right now, it is but only if everything is at the same Y-height.