Simplify XPlane CSL model strings

Before this change, the model strings were assembled via some
relatives pathes - long and very hard to read. Now it is assembled
via the pattern

<package root dir> <dir> ... <objectname> <texturename>

<package root dir> = the parent directory of xsb_aircrafts.txt
<dir> ... = directory hierarchy down to the object file

refs #574

src/blackmisc/simulation/xplane/aircraftmodelloaderxplane.h

@@ -69,7 +69,13 @@ namespace BlackMisc
             private:
                 struct CSLPlane
                 {
-                    QString modelName;  //!< Unique model name
+                    QString getModelName() const;
+
+                    // Model name parts
+                    QStringList dirNames; //!< List dir names starting from xsb_aircrafts.txt parent down to obj folder
+                    QString objectName;   //!< Complete basename of the object file
+                    QString textureName;  //!< Complete basename of the texture file
+
                     QString filePath;   //!< object filePath
                     QString icao;       //!< Icao type of this model
                     QString airline;    //!< Airline identifier. Can be empty.