Add functionality to save inference images for the debugging purposes.

Save bmp images of inference results to /tmp as bmp files. BMP was
chosen to reduce encoding time. Saving is fully threaded. It can be
enable with qmake CONFIG+=save_images option

Also:
  - use antialised fonts in RKNN inference
  - moved class strings to inference base class
  - fixed silly segfault in ONNX inference
  - prevent writing results if class if exceeds valid values

Issue: https://denyspopov.atlassian.net/browse/AZ-38
Type: Improvement

misc/rtsp_ai_player/aiengineinference.h

@@ -40,6 +40,7 @@ protected:
     QString mModelPath;
     bool mActive;
     int mNumber;
+    QVector<QString> mClassNames;
 
 public slots:
     virtual void performInferenceSlot(cv::Mat frame) = 0;