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/avairportlist.h

@@ -59,10 +59,10 @@ namespace BlackMisc
 
         protected:
             //! Myself
-            virtual const CAirportList &getContainer() const override { return *this; }
+            virtual const CAirportList &container() const override { return *this; }
 
             //! Myself
-            virtual CAirportList &getContainer() override { return *this; }
+            virtual CAirportList &container() override { return *this; }
 
         };
     } //namespace