Signal Keys for Circuit Networks

[MDReal]

I'd like to suggest a new optional "signal key" system for circuit networks.

Currently, circuit signals are identified only by a single signal type. This means signals of the same type are always merged together.

Example:

* Crude Oil = 50,000
* Crude Oil = 120,000

becomes:

* Crude Oil = 170,000

Instead, allow signals to optionally have one or two item-based keys, similar to the frequency system used by Redstone Links in the Create mod.

Examples:

* [Crude Oil | Iron Plate] = 50,000
* [Crude Oil | Copper Plate] = 120,000

or

* [Iron Ore | Outpost A] = 8,000
* [Iron Ore | Outpost B] = 12,000

Signals with different keys would remain separate while still using the same underlying signal type.

Possible uses:

* Global train dispatch systems
* Remote outpost monitoring
* Multi-base logistics networks
* Factory-wide telemetry systems
* Modded automation systems

The second key should be optional, allowing both normal signals and keyed signals to coexist.

This would significantly expand the capabilities of advanced circuit network designs without requiring new signal categories.