refs #369, changed interpolation to a working (but still too bad performing) version

* using split by callsign everywhere
* helper function to insert_front
* revised linear interpolator
* renamed to remoteAircraft
* renamed to container() in providers (gettters are usually copies)

Issues why changes did so long:
* insert in list is not adding in front, but same as push_back (that was confusing)
* naming of values before/after in interpolator was ambigious
* QMap keeps values sorted by key, not arbitrarily

src/blackmisc/aviation/aircraftparts.cpp

@@ -98,5 +98,15 @@ namespace BlackMisc
             }
         }
 
+        CAircraftEngine CAircraftParts::getEngine(int number) const
+        {
+            return this->m_engines.findBy(&CAircraftEngine::getNumber, number).frontOrDefault();
+        }
+
+        bool CAircraftParts::isEngineOn(int number) const
+        {
+            return this->getEngine(number).isOn();
+        }
+
     } // namespace
 } // namespace