SayIntentions: Use field flight_icao as callsign

[TwinFan]

Current Situation / Problem

The field callsign is "unprocessed" (convert from "Piper-two-Five-Seven-papa" back to "Piper 257P"), then used as callsign. But this never leads to a call sign that can be used for livery matching.

Suggested Solution

Use field flight_icao if available, which seems to hold a callsign as expected, like in the following record:

{
  "flight_id" : 842821721,
...
  "flight_icao" : "AAL2502",
  "callsign" : "American-two-five-zero-two",
  "tail_number" : "N123AZ",
...
}

The "unprocessed" callsign leads "American 2520" while just directly using flight_icao would use "AAL2502", which during livery matching would indeed find American Airlines liveries.

There are rare cases in which flight_icao and callsign don't agree, like in

{
  "flight_id" : 842822205,
  "flight_icao" : "SWR805G",
  "callsign" : "SWISS-One-Four-Two-six",
...
}

but these seem to be comparibly rare exceptions. The benefit of just using flight_icao when available outweights the risk of these rare mismatches.

Benefits

More appropriate representation of SI flights.

Additional context

Suggest in this forum post.

[TwinFan]

Works now in next version: