Reevaluate the Signal/Data separation in icsLang

[andrewbwm]

We currently have four assets dealing with the flow of data in icsLang:

IcsData - telemetry data over a known medium
IcsControlData - command data over a known medium
Signal - telemetry data over an unknown medium
ControlSignal - command data an unknown medium

I find this very confusing and I think that maybe we could remove the Signal and ControlSignal assets as they already mostly replicate the steps present in the Data asset. I am unsure why we need to have a distinct pair of assets for the situation where the medium is unknown, perhaps not having those assets connected to a Network asset would suffice.