Handle airport frequencies that are not defined in the database

[pierr3]

Some frequencies related to airports are not added in the AFV database by design, in this case, the client should create the frequency automatically with one transceiver set at the airport location.

Implementation suggested:

• Load in memory an airport database (see this repo)
• Add logic that if a station is not found, it needs to check if the ICAO exists in the airpot database, if it does, then it needs to create the frequency and change the client position to that airport location in afv_native
• Upon adding the frequency, AFV native will use the client position

See #5