Reflecting discussed changes for interpolation performance refs #386

(based on FSX testing)
* Only send changed situation to SIM
* Split sending of parts / situations
* Only send parts with a reduced frequency (means slower as positions)
* Mark geodetic height as null for default values (the value is usually unavailable)
* Fixed altitude to MSL for network data
* Trace which aircrafts support aircraft parts via network
* Renamed insert_fron push_front (as proposed by Roland)

Status quo / lessons learnt
* On slower PCs jitter is still noticed for interpolated aircraft.
* Running interpolation in an independent process (aka core, not in GUI) reduced load dependencies
  => it seems to make sense to run driver in own thread
* The onGround flag in parts seems clumsy as it required to retrieve parts for position updates
* In interpolation performance really matters

src/blackcore/interpolator_linear.h

@@ -30,7 +30,7 @@ namespace BlackCore
         {}
 
         //! \copydoc IInterpolator::getCurrentInterpolatedSituation
-        virtual BlackMisc::Aviation::CAircraftSituation getCurrentInterpolatedSituation(const QHash<BlackMisc::Aviation::CCallsign, BlackMisc::Aviation::CAircraftSituationList> &allSituations, const BlackMisc::Aviation::CCallsign &callsign, qint64 currentTimeSinceEpoc = -1, bool *ok = nullptr) const override;
+        virtual BlackMisc::Aviation::CAircraftSituation getInterpolatedSituation(const BlackMisc::Aviation::CCallsign &callsign, qint64 currentTimeSinceEpoc, InterpolationStatus &status, const CSituationsPerCallsign *situationsPerCallsign = nullptr) const override;
 
         //! Log category
         static QString getMessageCategory() { return "swift.interpolatorlinear"; }