add estimated center points for ATC stations

[dneuge]

Online controllers no longer have coordinates in JSON v3. Applications such as QuteScoop depend on coordinates to display unknown stations but also to position labels on known stations.

https://github.com/vatsimnetwork/vatspy-data-project could be used for static airspace/controller information. Center points could then be calculated and injected by the proxy. Parsing and entities should be added to https://github.com/vatplanner/dataformats-vatsim-public

[dneuge]

Apparently AFV transceivers are public API now: https://api.vatsim.dev/#operation/TransceiverData

Since every controller is supposed to provide voice service that information could also be used to calculate a controller position. There are a few downsides however:

• the URL is currently only advertised through API docs, it is not listed on https://status.vatsim.net/status.json nor https://status.vatsim.net/status.txt
• it would need to be fetched "together" with JSON data files and may be out of sync

[dneuge]

VAT-Spy parsing support has been added to VATPlanner library.

[dneuge]

Transceivers will probably not be added to the upcoming release as I don't want to delay a first version with VAT-Spy any further which has already worked fine in the development version for 2 weeks now and before VATSIM clarified how the transceivers list is supposed to be used. VAT-Spy data alone provides very good matches already (observed: at most 3 stations missing at any time), so further delay makes no sense.

Tracking transceivers in #7.

[dneuge]

VAT-Spy location feature released with 0.90.