Added AirMap settings (SettingsGroup)
Added AirMap settings block to General Settings
Create macros to deal with the tedious repetitions within SettingsGroup
Removed old, hacked in setting for AirMapKey
Remove a few of the tons of build warnings

This includes polling for a flight permission.
The steps are:
- get pilot id (new API requires to provide it, even though it does not
  make much sense)
- create a flight plan
- call the briefing (to check if SITA registration id's are valid)
- call the submit -> returns the actual flight id
- poll on the briefing until the flight gets approved

Since there can only be one flight, on startup, we list the pilot's flights
and end the one that ends in future

- start telemetry if there's a valid flight id and the vehicle armed
- only the Position message is sent for now

Requires protobuf to be installed on the build system

This is just to test, will need much better integration

Nope, it's microseconds alright. The autopilot I was testing with indeed only had 19 seconds of "armed" time.