refs #643, moved aircraft model icon loading to model class

* removed iconForModel from interface and aircraft config parser
* CPixmap support for loading pixmap from file
* Access to model of model set loader by model string
* icon path as member of CAircraftModel

src/blackmisc/simulation/fscommon/aircraftcfgentries.cpp

@@ -120,6 +120,7 @@ namespace BlackMisc
                 model.setFileName(this->getFileName());
                 model.setName(this->getSimName());
                 model.setUtcTimestamp(this->getUtcTimestamp()); // aircraft.cfg file last modified
+                model.setIconPath(this->getThumbnailFileName());
 
                 const QString designator(CAircraftIcaoCode::normalizeDesignator(getAtcModel()));
                 CAircraftIcaoCode aircraft(