* Before this commit, only the true altitude was known for an aircraft situation. The pressure altitude was not available anywhere yet.
* This caused a wrong altitude in radar clients.
* We fix this reading the pressure altitude from the simulators and set it in the own aircraft situation.
* MS Flight Simulators have the pressure altitude in the APIs available.
* For X-Plane and emulated simulator, we need to calculate it from the pressure at sea level.
* Finally, we use the new available pressure altitude to send it to the FSD server.
Maniphest Tasks: Ref T223
In same step cleaned up contexts a bit
* added function for model set strings
* renamed functions to getModelSet... instead of installed models (the set is smaller and is what we want to use with DBus)
* signal when debug/log flags changed
* removed some \copydoc
* allow to enable/disable rev.lookup/matching messages
* removed reload model function (dangling)
